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  • Filling array with numbers from given range so that sum of adjacent numbers is square number

    - by REACHUS
    Problem: Fill all the cells using distinct numbers from <1,25 set, so that sum of two adjacent cells is a square number. (source: http://grymat.im.pwr.wroc.pl/etap1/zad1etp1213.pdf; numbers 20 and 13 have been given) I've already solved this problem analytically and now I would like to approach it using an algorithm. I would like to know how should I approach these kind of problems in general (not a solution, just a point for me to start).

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  • Complex.pm taking up a lot of time

    - by synapz
    While trying to profile my perl program, I find that Complex.pm is taking up a lot of time with what looks like some kind of warning. Also, my code shouldn't have any complex numbers being generated or used, so I am not sure what it is doing in Complex.pm, anyway. Here's the FastProf output for the most expensive lines: /usr/lib/perl5/5.8.8/Math/Complex.pm:182 1.55480 276232: _cannot_make("real part", $re) unless $re =~ /^$gre$/; /usr/lib/perl5/5.8.8/Math/Complex.pm:310 1.01132 453641: sub cartesian {$_[0]->{c_dirty} ? /usr/lib/perl5/5.8.8/Math/Complex.pm:315 0.97497 562188: sub set_cartesian { $_[0]->{p_dirty}++; $_[0]->{c_dirty} = 0; /usr/lib/perl5/5.8.8/Math/Complex.pm:189 0.86302 276232: return $self; /usr/lib/perl5/5.8.8/Math/Complex.pm:1332 0.85628 293660: $self->{display_format} = { %display_format }; /usr/lib/perl5/5.8.8/Math/Complex.pm:185 0.81529 276232: _cannot_make("imaginary part", $im) unless $im =~ /^$gre$/; /usr/lib/perl5/5.8.8/Math/Complex.pm:1316 0.78749 293660: my %display_format = %DISPLAY_FORMAT; /usr/lib/perl5/5.8.8/Math/Complex.pm:1335 0.69534 293660: %{$self->{display_format}} : /usr/lib/perl5/5.8.8/Math/Complex.pm:186 0.66697 276232: $self->set_cartesian([$re, $im ]); /usr/lib/perl5/5.8.8/Math/Complex.pm:170 0.62790 276232: my $self = bless {}, shift; /usr/lib/perl5/5.8.8/Math/Complex.pm:172 0.56733 276232: if (@_ == 0) { /usr/lib/perl5/5.8.8/Math/Complex.pm:316 0.53179 281094: $_[0]->{'cartesian'} = $_[1] } /usr/lib/perl5/5.8.8/Math/Complex.pm:1324 0.48768 293660: if (@_ == 1) { /usr/lib/perl5/5.8.8/Math/Complex.pm:1319 0.44835 293660: if (exists $self->{display_format}) { /usr/lib/perl5/5.8.8/Math/Complex.pm:1318 0.40355 293660: if (ref $self) { # Called as an object method /usr/lib/perl5/5.8.8/Math/Complex.pm:187 0.39950 276232: $self->display_format('cartesian'); /usr/lib/perl5/5.8.8/Math/Complex.pm:1315 0.39312 293660: my $self = shift; /usr/lib/perl5/5.8.8/Math/Complex.pm:1331 0.38087 293660: if (ref $self) { # Called as an object method /usr/lib/perl5/5.8.8/Math/Complex.pm:184 0.35171 276232: $im ||= 0; /usr/lib/perl5/5.8.8/Math/Complex.pm:181 0.34145 276232: if (defined $re) { /usr/lib/perl5/5.8.8/Math/Complex.pm:171 0.33492 276232: my ($re, $im); /usr/lib/perl5/5.8.8/Math/Complex.pm:390 0.20658 128280: my ($z1, $z2, $regular) = @_; /usr/lib/perl5/5.8.8/Math/Complex.pm:391 0.20631 128280: if ($z1->{p_dirty} == 0 and ref $z2 and $z2->{p_dirty} == 0) { Thanks for any help!

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  • How to add in in appendix page numbers separately from the regular heading page numbers

    - by O_O
    I had regular page numbers on my Microsoft Word 2007 document at the bottom center of my page, starting from 1 from Insert tab Page Number Bottom of page Plain Number 2. I added an appendix with Heading 6 and followed the instructions from http://support.microsoft.com/kb/290953 to create separate page numbers just for the appendix, i.e. A-1, A-2, B-1, B-2, etc. The Page Number Format configuration I did is here: ]When I try to set this however, it changes all of the page numbers to this format, even the ones that aren't from heading 6 (meaning it changes the non-appendix content to this page number format). Here's another example: 1 Heading1 has page number A-4 (note it starts at A-1 at the title page) ... Appendix A has page number A-12 I would like to change it so that 1 Heading1 has page number 4 (note it starts at 1 at the title page) ... Appendix A has page number A-1 Anyone know why this is happening? Thank you!!

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  • Precision of cos(atan2(y,x)) versus using complex <double>, C++

    - by Ivan
    Hi all, I'm writing some coordinate transformations (more specifically the Joukoswky Transform, Wikipedia Joukowsky Transform), and I'm interested in performance, but of course precision. I'm trying to do the coordinate transformations in two ways: 1) Calculating the real and complex parts in separate, using double precision, as below: double r2 = chi.x*chi.x + chi.y*chi.y; //double sq = pow(r2,-0.5*n) + pow(r2,0.5*n); //slow!!! double sq = sqrt(r2); //way faster! double co = cos(atan2(chi.y,chi.x)); double si = sin(atan2(chi.y,chi.x)); Z.x = 0.5*(co*sq + co/sq); Z.y = 0.5*si*sq; where chi and Z are simple structures with double x and y as members. 2) Using complex : Z = 0.5 * (chi + (1.0 / chi)); Where Z and chi are complex . There interesting part is that indeed the case 1) is faster (about 20%), but the precision is bad, giving error in the third decimal number after the comma after the inverse transform, while the complex gives back the exact number. So, the problem is on the cos(atan2), sin(atan2)? But if it is, how the complex handles that? Thanks!

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  • The Numerical ‘Magic’ of Cyclic Numbers

    - by Akemi Iwaya
    If you love crunching numbers or are just a fan of awesome number ‘tricks’ to impress your friends with, then you will definitely want to have a look at cyclic numbers. Dr Tony Padilla from the University of Nottingham shows how these awesome numbers work in Numberphile’s latest video. Cyclic Numbers – Numberphile [YouTube] Want to learn more about cyclic numbers? Then make sure to visit the Wikipedia page linked below! Cyclic number [Wikipedia]     

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  • Password Security: Short and Complex versus ‘Short or Lengthy’ and Less Complex

    - by Akemi Iwaya
    Creating secure passwords for our online accounts is a necessary evil due to the huge increase in database and account hacking that occurs these days. The problem though is that no two companies have a similar policy for complex and secure password creation, then factor in the continued creation of insecure passwords or multi-site use of the same password and trouble is just waiting to happen. Ars Technica decided to take a look at multiple password types, how users fared with them, and how well those password types held up to cracking attempts in their latest study. The password types that Ars Technica looked at were comprehensive8, basic8, and basic16. The comprehensive type required a variety of upper-case, lower-case, digits, and symbols with no dictionary words allowed. The only restriction on the two basic types was the number of characters used. Which type do you think was easier for users to adopt and did better in the two password cracking tests? You can learn more about how well users did with the three password types and the results of the tests by visiting the article linked below. What are your thoughts on the matter? Are shorter, more complex passwords better or worse than using short or long, but less complex passwords? What methods do you feel work best since most passwords are limited to approximately 16 characters in length? Perhaps you use a service like LastPass or keep a dedicated list/notebook to manage your passwords. Let us know in the comments!    

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  • C code won't compile

    - by cc
    Please help me to understand why the following code will not compile: #include <stdio.h> //#include <iostream> //using namespace std; int main(void){ int i,k,x,y,run,e,r,s,m,count=0; char numbers[19][19]; for(i=0;i<19;i++){ for (k=0;k<19;k++){ numbers[i][k]='.'; } } void drawB(){ printf(" 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 \n"); printf ("0 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[0][0],numbers[0][1],numbers[0][2],numbers[0][3],numbers[0][4], numbers[0][5],numbers[0][6],numbers[0][7],numbers[0][8],numbers[0][9], numbers[0][10],numbers[1][11],numbers[1][12],numbers[1][13],numbers[0][14] ,numbers[0][15],numbers[0][16],numbers[0][17],numbers[0][18]); printf ("1 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[1][0],numbers[1][1],numbers[1][2],numbers[1][3],numbers[1][4], numbers[1][5],numbers[1][6],numbers[1][7],numbers[1][8],numbers[1][9], numbers[1][10],numbers[1][11],numbers[1][12],numbers[1][13],numbers[1][14] ,numbers[1][15],numbers[1][16],numbers[1][17],numbers[1][18]); printf ("2 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" numbers[2][0],numbers[2][1],numbers[2][2],numbers[2][3],numbers[2][4], numbers[2][5],numbers[2][6],numbers[2][7],numbers[2][8],numbers[2][9], numbers[2][10],numbers[2][11],numbers[2][12],numbers[2][13],numbers[2][14] ,numbers[2][15],numbers[2][16],numbers[2][17],numbers[2][18]); printf ("3 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[3][0],numbers[3][1],numbers[3][2],numbers[3][3],numbers[3][4], numbers[3][5],numbers[3][6],numbers[3][7],numbers[3][8],numbers[3][9], numbers[3][10],numbers[3][11],numbers[3][12],numbers[3][13],numbers[3][14] ,numbers[3][15],numbers[3][16],numbers[3][17],numbers[3][18]); printf ("4 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[4][0],numbers[4][1],numbers[4][2],numbers[4][3],numbers[4][4], numbers[4][5],numbers[4][6],numbers[4][7],numbers[4][8],numbers[4][9], numbers[4][10],numbers[4][11],numbers[4][12],numbers[4][13],numbers[4][14] ,numbers[4][15],numbers[4][16],numbers[4][17],numbers[4][18]); printf ("5 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[5][0],numbers[5][1],numbers[5][2],numbers[5][3],numbers[5][4], numbers[5][5],numbers[5][6],numbers[5][7],numbers[5][8],numbers[5][9], numbers[5][10],numbers[5][11],numbers[5][12],numbers[5][13],numbers[5][14] ,numbers[5][15],numbers[5][16],numbers[5][17],numbers[5][18]); printf ("6 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[6][0],numbers[6][1],numbers[6][2],numbers[6][3],numbers[6][4], numbers[6][5],numbers[6][6],numbers[6][7],numbers[6][8],numbers[6][9], numbers[6][10],numbers[6][11],numbers[6][12],numbers[6][13],numbers[6][14] ,numbers[6][15],numbers[6][16],numbers[6][17],numbers[6][18]); printf ("7 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[7][0],numbers[7][1],numbers[7][2],numbers[7][3],numbers[7][4], numbers[7][5],numbers[7][6],numbers[7][7],numbers[7][8],numbers[7][9], numbers[7][10],numbers[7][11],numbers[7][12],numbers[7][13],numbers[7][14] ,numbers[7][15],numbers[7][16],numbers[7][17],numbers[7][18]); printf ("8 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[8][0],numbers[8][1],numbers[8][2],numbers[8][3],numbers[8][4], numbers[8][5],numbers[8][6],numbers[8][7],numbers[8][8],numbers[8][9], numbers[8][10],numbers[8][11],numbers[8][12],numbers[8][13],numbers[8][14] ,numbers[8][15],numbers[8][16],numbers[8][17],numbers[8][18]); printf ("9 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[9][0],numbers[9][1],numbers[9][2],numbers[9][3],numbers[9][4], numbers[9][5],numbers[9][6],numbers[9][7],numbers[9][8],numbers[9][9], numbers[9][10],numbers[9][11],numbers[9][12],numbers[9][13],numbers[9][14] ,numbers[9][15],numbers[9][16],numbers[9][17],numbers[9][18]); printf ("0 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[10][0],numbers[10][1],numbers[10][2],numbers[10][3],numbers[10][4], numbers[10][5],numbers[10][6],numbers[10][7],numbers[10][8],numbers[10][9], numbers[10][10],numbers[10][11],numbers[10][12],numbers[10][13],numbers[10][14] ,numbers[10][15],numbers[10][16],numbers[10][17],numbers[10][18]); printf ("1 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[11][0],numbers[11][1],numbers[11][2],numbers[11][3],numbers[11][4], numbers[11][5],numbers[11][6],numbers[11][7],numbers[11][8],numbers[11][9], numbers[11][10],numbers[11][11],numbers[11][12],numbers[11][13],numbers[11][14] ,numbers[11][15],numbers[11][16],numbers[11][17],numbers[11][18]); printf ("2 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[12][0],numbers[12][1],numbers[12][2],numbers[12][3],numbers[12][4], numbers[12][5],numbers[12][6],numbers[12][7],numbers[12][8],numbers[12][9], numbers[12][10],numbers[12][11],numbers[12][12],numbers[12][13],numbers[12][14] ,numbers[12][15],numbers[12][16],numbers[12][17],numbers[12][18]); printf ("3 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[13][0],numbers[13][1],numbers[13][2],numbers[13][3],numbers[13][4], numbers[13][5],numbers[13][6],numbers[13][7],numbers[13][8],numbers[13][9], numbers[13][10],numbers[13][11],numbers[13][12],numbers[13][13],numbers[13][14] ,numbers[13][15],numbers[13][16],numbers[13][17],numbers[13][18]); printf ("4 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[14][0],numbers[14][1],numbers[14][2],numbers[14][3],numbers[14][4], numbers[14][5],numbers[14][6],numbers[14][7],numbers[14][8],numbers[14][9], numbers[14][10],numbers[14][11],numbers[14][12],numbers[14][13],numbers[14][14] ,numbers[14][15],numbers[14][16],numbers[14][17],numbers[14][18]); printf ("5 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[15][0],numbers[15][1],numbers[15][2],numbers[15][3],numbers[15][4], numbers[15][5],numbers[15][6],numbers[15][7],numbers[15][8],numbers[15][9], numbers[15][10],numbers[15][11],numbers[15][12],numbers[15][13],numbers[15][14] ,numbers[15][15],numbers[15][16],numbers[15][17],numbers[15][18]); printf ("6 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[16][0],numbers[16][1],numbers[16][2],numbers[16][3],numbers[16][4], numbers[16][5],numbers[16][6],numbers[16][7],numbers[16][8],numbers[16][9], numbers[16][10],numbers[16][11],numbers[16][12],numbers[16][13],numbers[16][14] ,numbers[16][15],numbers[16][16],numbers[16][17],numbers[16][18]); printf ("7 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[17][0],numbers[17][1],numbers[17][2],numbers[17][3],numbers[17][4], numbers[17][5],numbers[17][6],numbers[17][7],numbers[17][8],numbers[17][9], numbers[17][10],numbers[17][11],numbers[17][12],numbers[17][13],numbers[17][14] ,numbers[17][15],numbers[17][16],numbers[17][17],numbers[17][18]); printf ("8 %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c %c \n\n" ,numbers[18][0],numbers[18][1],numbers[18][2],numbers[18][3],numbers[18][4], numbers[18][5],numbers[18][6],numbers[18][7],numbers[18][8],numbers[18][9], numbers[18][10],numbers[18][11],numbers[18][12],numbers[18][13],numbers[18][14] ,numbers[18][15],numbers[18][16],numbers[18][17],numbers[18][18]); } void checkSurrounded (int x,int y){ //numbers [x-1,y-1 ] , numbers [x-1,y ] , numbers [x-1,y+1 ] //numbers [x,y-1 ] , numbers [x,y ] , numbers [x,y+1 ] //numbers [x+1,y-1, ] , numbers [x+1,y ] , numbers [x+1,y+1 ] if(numbers[x][y]=='A'){ if((numbers[x-1][y-1]=='B') && (numbers[x-1][y]=='B') && (numbers[x-1][y+1]=='B') && (numbers[x][y-1]=='B') && (numbers[x][y+1]=='B') && (numbers[x+1][y-1]=='B') && (numbers[x+1][y]=='B')){ numbers[x][y]='B';} } if(numbers[x][y]=='B'){ if((numbers[x-1][y-1]=='A') && (numbers[x-1][y]=='A') && (numbers[x-1][y+1]=='A') && (numbers[x][y-1]=='A') && (numbers[x][y+1]=='A') && (numbers[x+1][y-1]=='A') && (numbers[x+1][y]=='A')){ numbers[x][y]='A'; } } } /** void checkArea(){ //detect enemy stone //store in array //find adjacent enemy stones // store the enemy stones in the array //keep on doing this until there are no more enemy stones that are adjacent for (s=0;s<19;s++) { for (m=0;m<19;m++) { if (numbers[s][m]=='A'){ count++; } } } }//end fn void checkAdjacent(int x, int y){ if (numbers [x][y]=='A'){ if((numbers[x][y-1]=='B' && numbers [x-1][y]=='B' && numbers[x][y+1]=='B' && numbers[x+1][y]=='B')){ } } } void getUserInput(){ int run=1; while(run){ printf("Enter x coordinate\n"); scanf("%d",&x); printf("Enter y coordinate\n"); scanf("%d",&y); if((x>18 || y>18 || x<0 || y<0) && !( numbers[x][y]=='.' )){ printf("invalid imput\n"); } else{ numbers[x][y]='B'; run=0; drawB(); } } } */ void getCupInput(){ //go through borad //starting from [0][0] //stop at first player stone //save as target x and target y //surround target x and target y //if already surrounded //start looking in borad again from last position //at end of board reset to [0][0] for(s=0;s<19;s++) { for(m=0;m<19;m++) { if (numbers[s][m]==0){ count++; } } } x=x-2; y=y+2; numbers[x][y]='A'; drawB(); } while(1){ //getUserInput(); getCupInput(); } system("pause"); return 0; }

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  • Generate n-dimensional random numbers in Python

    - by Magsol
    I'm trying to generate random numbers from a gaussian distribution. Python has the very useful random.gauss() method, but this is only a one-dimensional random variable. How could I programmatically generate random numbers from this distribution in n-dimensions? For example, in two dimensions, the return value of this method is essentially distance from the mean, so I would still need (x,y) coordinates to determine an actual data point. I suppose I could generate two more random numbers, but I'm not sure how to set up the constraints. I appreciate any insights. Thanks!

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  • Complex algorithm for complex problem

    - by Locaaaaa
    I got this question in an interview and I was not able to solve it. You have a circular road, with N number of gas stations. You know the ammount of gas that each station has. You know the ammount of gas you need to GO from one station to the next one. Your car starts with 0. The question is: Create an algorithm, to know from which gas station you must start driving. As an exercise to me, I would translate the algorithm to C#.

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  • The Most Common and Least Used 4-Digit PIN Numbers [Security Analysis Report]

    - by Asian Angel
    How ‘secure’ is your 4-digit PIN number? Is your PIN number a far too common one or is it a bit more unique in comparison to others? The folks over at the Data Genetics blog have put together an interesting analysis report that looks at the most common and least used 4-digit PIN numbers chosen by people. Numerically based (0-9) 4-digit PIN numbers only allow for a total of 10,000 possible combinations, so it stands to reason that some combinations are going to be far more common than others. The question is whether or not your personal PIN number choices are among the commonly used ones or ‘stand out’ as being more unique. Note 1: Data Genetics used data condensed from released, exposed, & discovered password tables and security breaches to generate the analysis report. Note 2: The updates section at the bottom has some interesting tidbits concerning peoples’ use of dates and certain words for PIN number generation. The analysis makes for very interesting reading, so browse on over to get an idea of where you stand with regards to your personal PIN number choices. 8 Deadly Commands You Should Never Run on Linux 14 Special Google Searches That Show Instant Answers How To Create a Customized Windows 7 Installation Disc With Integrated Updates

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  • Two different page numbers in Word 2007 (one starting at 1, the other at VI)

    - by user1251007
    I have a document (docA) with arabic page numbers in the header. Now docA is part of a thesis which has roman numbers in the footer. So I want to add roman page numbers to docA. This is no problem. But now I want to adjust the numbering of the roman numbers (as the thesis has lets say five pages). This is what I want: arabic page numbers in the header, starting at 1 roman page numbers in the footer, starting at VI I tried this: I choosed 'Page Number', 'Page Number Format' and tried to adjust the starting point. However, this changes both page numbers. How is it possible to have different numbering in the header and in the footer?

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  • Why is it impossible to produce truly random numbers?

    - by Vinoth Kumar
    I was trying to solve a hobby problem that required generating a million random numbers. But I quickly realized, it is becoming difficult to make them unique. I picked up Algorithm Design Manual to read about random number generation. It has the following paragraph that I am fully not able to understand. Unfortunately, generating random numbers looks a lot easier than it really is. Indeed, it is fundamentally impossible to produce truly random numbers on any deterministic device. Von Neumann [Neu63] said it best: “Anyone who considers arithmetical methods of producing random digits is, of course, in a state of sin.” The best we can hope for are pseudo-random numbers, a stream of numbers that appear as if they were generated randomly. Why is it impossible to produce truly random numbers in any deterministic device? What does this sentence mean?

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  • How do functional languages handle random numbers?

    - by Electric Coffee
    What I mean about that is that in nearly every tutorial I've read about functional languages, is that one of the great things about functions, is that if you call a function with the same parameters twice, you'll always end up with the same result. How on earth do you then make a function that takes a seed as a parameter, and then returns a random number based on that seed? I mean this would seem to go against one of the things that are so good about functions, right? Or am I completely missing something here?

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  • Understanding binary numbers in terms of real world objects

    - by Kaushik
    When I represent a number in the decimal system, I have an intuitive knowledge of what it amounts to. For example take the number '10': I understand that it means 10 apples or 10 people... i.e I can count in the real world. But as soon as the number is converted to any other system, this understanding no longer applies. For example 10 when converted to binary will be 1010...now what does this represent? Is there a way to understand this number 1010 in terms of counting objects in the real world?

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  • Oracle Data Integrator 11.1.1.5 Complex Files as Sources and Targets

    - by Alex Kotopoulis
    Overview ODI 11.1.1.5 adds the new Complex File technology for use with file sources and targets. The goal is to read or write file structures that are too complex to be parsed using the existing ODI File technology. This includes: Different record types in one list that use different parsing rules Hierarchical lists, for example customers with nested orders Parsing instructions in the file data, such as delimiter types, field lengths, type identifiers Complex headers such as multiple header lines or parseable information in header Skipping of lines  Conditional or choice fields Similar to the ODI File and XML File technologies, the complex file parsing is done through a JDBC driver that exposes the flat file as relational table structures. Complex files are mapped to one or more table structures, as opposed to the (simple) file technology, which always has a one-to-one relationship between file and table. The resulting set of tables follows the same concept as the ODI XML driver, table rows have additional PK-FK relationships to express hierarchy as well as order values to maintain the file order in the resulting table.   The parsing instruction format used for complex files is the nXSD (native XSD) format that is already in use with Oracle BPEL. This format extends the XML Schema standard by adding additional parsing instructions to each element. Using nXSD parsing technology, the native file is converted into an internal XML format. It is important to understand that the XML is streamed to improve performance; there is no size limitation of the native file based on memory size, the XML data is never fully materialized.  The internal XML is then converted to relational schema using the same mapping rules as the ODI XML driver. How to Create an nXSD file Complex file models depend on the nXSD schema for the given file. This nXSD file has to be created using a text editor or the Native Format Builder Wizard that is part of Oracle BPEL. BPEL is included in the ODI Suite, but not in standalone ODI Enterprise Edition. The nXSD format extends the standard XSD format through nxsd attributes. NXSD is a valid XML Schema, since the XSD standard allows extra attributes with their own namespaces. The following is a sample NXSD schema: <?xml version="1.0"?> <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:nxsd="http://xmlns.oracle.com/pcbpel/nxsd" elementFormDefault="qualified" xmlns:tns="http://xmlns.oracle.com/pcbpel/demoSchema/csv" targetNamespace="http://xmlns.oracle.com/pcbpel/demoSchema/csv" attributeFormDefault="unqualified" nxsd:encoding="US-ASCII" nxsd:stream="chars" nxsd:version="NXSD"> <xsd:element name="Root">         <xsd:complexType><xsd:sequence>       <xsd:element name="Header">                 <xsd:complexType><xsd:sequence>                         <xsd:element name="Branch" type="xsd:string" nxsd:style="terminated" nxsd:terminatedBy=","/>                         <xsd:element name="ListDate" type="xsd:string" nxsd:style="terminated" nxsd:terminatedBy="${eol}"/>                         </xsd:sequence></xsd:complexType>                         </xsd:element>                 </xsd:sequence></xsd:complexType>         <xsd:element name="Customer" maxOccurs="unbounded">                 <xsd:complexType><xsd:sequence>                 <xsd:element name="Name" type="xsd:string" nxsd:style="terminated" nxsd:terminatedBy=","/>                         <xsd:element name="Street" type="xsd:string" nxsd:style="terminated" nxsd:terminatedBy="," />                         <xsd:element name="City" type="xsd:string" nxsd:style="terminated" nxsd:terminatedBy="${eol}" />                         </xsd:sequence></xsd:complexType>                         </xsd:element>                 </xsd:sequence></xsd:complexType> </xsd:element> </xsd:schema> The nXSD schema annotates elements to describe their position and delimiters within the flat text file. The schema above uses almost exclusively the nxsd:terminatedBy instruction to look for the next terminator chars. There are various constructs in nXSD to parse fixed length fields, look ahead in the document for string occurences, perform conditional logic, use variables to remember state, and many more. nXSD files can either be written manually using an XML Schema Editor or created using the Native Format Builder Wizard. Both Native Format Builder Wizard as well as the nXSD language are described in the Application Server Adapter Users Guide. The way to start the Native Format Builder in BPEL is to create a new File Adapter; in step 8 of the Adapter Configuration Wizard a new Schema for Native Format can be created:   The Native Format Builder guides through a number of steps to generate the nXSD based on a sample native file. If the format is complex, it is often a good idea to “approximate” it with a similar simple format and then add the complex components manually.  The resulting *.xsd file can be copied and used as the format for ODI, other BPEL constructs such as the file adapter definition are not relevant for ODI. Using this technique it is also possible to parse the same file format in SOA Suite and ODI, for example using SOA for small real-time messages, and ODI for large batches. This nXSD schema in this example describes a file with a header row containing data and 3 string fields per row delimited by commas, for example: Redwood City Downtown Branch, 06/01/2011 Ebeneezer Scrooge, Sandy Lane, Atherton Tiny Tim, Winton Terrace, Menlo Park The ODI Complex File JDBC driver exposes the file structure through a set of relational tables with PK-FK relationships. The tables for this example are: Table ROOT (1 row): ROOTPK Primary Key for root element SNPSFILENAME Name of the file SNPSFILEPATH Path of the file SNPSLOADDATE Date of load Table HEADER (1 row): ROOTFK Foreign Key to ROOT record ROWORDER Order of row in native document BRANCH Data BRANCHORDER Order of Branch within row LISTDATE Data LISTDATEORDER Order of ListDate within row Table ADDRESS (2 rows): ROOTFK Foreign Key to ROOT record ROWORDER Order of row in native document NAME Data NAMEORDER Oder of Name within row STREET Data STREETORDER Order of Street within row CITY Data CITYORDER Order of City within row Every table has PK and/or FK fields to reflect the document hierarchy through relationships. In this example this is trivial since the HEADER and all CUSTOMER records point back to the PK of ROOT. Deeper nested documents require this to identify parent elements. All tables also have a ROWORDER field to define the order of rows, as well as order fields for each column, in case the order of columns varies in the original document and needs to be maintained. If order is not relevant, these fields can be ignored. How to Create an Complex File Data Server in ODI After creating the nXSD file and a test data file, and storing it on the local file system accessible to ODI, you can go to the ODI Topology Navigator to create a Data Server and Physical Schema under the Complex File technology. This technology follows the conventions of other ODI technologies and is very similar to the XML technology. The parsing settings such as the source native file, the nXSD schema file, the root element, as well as the external database can be set in the JDBC URL: The use of an external database defined by dbprops is optional, but is strongly recommended for production use. Ideally, the staging database should be used for this. Also, when using a complex file exclusively for read purposes, it is recommended to use the ro=true property to ensure the file is not unnecessarily synchronized back from the database when the connection is closed. A data file is always required to be present  at the filename path during design-time. Without this file, operations like testing the connection, reading the model data, or reverse engineering the model will fail.  All properties of the Complex File JDBC Driver are documented in the Oracle Fusion Middleware Connectivity and Knowledge Modules Guide for Oracle Data Integrator in Appendix C: Oracle Data Integrator Driver for Complex Files Reference. David Allan has created a great viewlet Complex File Processing - 0 to 60 which shows the creation of a Complex File data server as well as a model based on this server. How to Create Models based on an Complex File Schema Once physical schema and logical schema have been created, the Complex File can be used to create a Model as if it were based on a database. When reverse-engineering the Model, data stores(tables) for each XSD element of complex type will be created. Use of complex files as sources is straightforward; when using them as targets it has to be made sure that all dependent tables have matching PK-FK pairs; the same applies to the XML driver as well. Debugging and Error Handling There are different ways to test an nXSD file. The Native Format Builder Wizard can be used even if the nXSD wasn’t created in it; it will show issues related to the schema and/or test data. In ODI, the nXSD  will be parsed and run against the existing test XML file when testing a connection in the Dataserver. If either the nXSD has an error or the data is non-compliant to the schema, an error will be displayed. Sample error message: Error while reading native data. [Line=1, Col=5] Not enough data available in the input, when trying to read data of length "19" for "element with name D1" from the specified position, using "style" as "fixedLength" and "length" as "". Ensure that there is enough data from the specified position in the input. Complex File FAQ Is the size of the native file limited by available memory? No, since the native data is streamed through the driver, only the available space in the staging database limits the size of the data. There are limits on individual field sizes, though; a single large object field needs to fit in memory. Should I always use the complex file driver instead of the file driver in ODI now? No, use the file technology for all simple file parsing tasks, for example any fixed-length or delimited files that just have one row format and can be mapped into a simple table. Because of its narrow assumptions the ODI file driver is easy to configure within ODI and can stream file data without writing it into a database. The complex file driver should be used whenever the use case cannot be handled through the file driver. Are we generating XML out of flat files before we write it into a database? We don’t materialize any XML as part of parsing a flat file, either in memory or on disk. The data produced by the XML parser is streamed in Java objects that just use XSD-derived nXSD schema as its type system. We use the nXSD schema because is the standard for describing complex flat file metadata in Oracle Fusion Middleware, and enables users to share schemas across products. Is the nXSD file interchangeable with SOA Suite? Yes, ODI can use the same nXSD files as SOA Suite, allowing mixed use cases with the same data format. Can I start the Native Format Builder from the ODI Studio? No, the Native Format Builder has to be started from a JDeveloper with BPEL instance. You can get BPEL as part of the SOA Suite bundle. Users without SOA Suite can manually develop nXSD files using XSD editors. When is the database data written back to the native file? Data is synchronized using the SYNCHRONIZE and CREATE FILE commands, and when the JDBC connection is closed. It is recommended to set the ro or read_only property to true when a file is exclusively used for reading so that no unnecessary write-backs occur. Is the nXSD metadata part of the ODI Master or Work Repository? No, the data server definition in the master repository only contains the JDBC URL with file paths; the nXSD files have to be accessible on the file systems where the JDBC driver is executed during production, either by copying or by using a network file system. Where can I find sample nXSD files? The Application Server Adapter Users Guide contains nXSD samples for various different use cases.

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  • trying to divide complex numbers, division by zero

    - by user553619
    I'm trying the program below to divide complex numbers, it works for complex numbers but not when the denominator is real (i.e, the complex part is zero). Division by zero occurs in this line ratio = b->r / b->i ;, when the complex part b->i is zero (in the case of a real denominator). How do I get around this? and why did the programmer do this, instead of the more straightforward rule for complex division The wikipedia rule seems to be better, and no division by zero error would occur here. Did I miss something? Why did the programmer not use the wikipedia formula?? Thanks /*! @file dcomplex.c * \brief Common arithmetic for complex type * * <pre> * -- SuperLU routine (version 2.0) -- * Univ. of California Berkeley, Xerox Palo Alto Research Center, * and Lawrence Berkeley National Lab. * November 15, 1997 * * This file defines common arithmetic operations for complex type. * </pre> */ #include <math.h> #include <stdlib.h> #include <stdio.h> #include "slu_dcomplex.h" /*! \brief Complex Division c = a/b */ void z_div(doublecomplex *c, doublecomplex *a, doublecomplex *b) { double ratio, den; double abr, abi, cr, ci; if( (abr = b->r) < 0.) abr = - abr; if( (abi = b->i) < 0.) abi = - abi; if( abr <= abi ) { if (abi == 0) { fprintf(stderr, "z_div.c: division by zero\n"); exit(-1); } ratio = b->r / b->i ; den = b->i * (1 + ratio*ratio); cr = (a->r*ratio + a->i) / den; ci = (a->i*ratio - a->r) / den; } else { ratio = b->i / b->r ; den = b->r * (1 + ratio*ratio); cr = (a->r + a->i*ratio) / den; ci = (a->i - a->r*ratio) / den; } c->r = cr; c->i = ci; }

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  • Paste a list of dates in format of "mm/dd/yy" to iWork-Numbers

    - by David.Chu.ca
    I have trouble to paste a list of strings in the format of 'mm/dd/yy' into iWork-Numbers. For example, I have a list of strings(text in VIM): 04/01/10 04/03/10 04/13/10 I copy those strings and then paste into my iWork-Numbers worksheet. The result will be: 2004-01-10 2004-03-10 04/13/10 It looks like that Numbers (mac workseet application in iWork) tries to convert the first two digits into year, then the next two into month if less than 12 and last two digits to a day, for the first two rows. For the third(04/13/10), since the middle two digits are 13 and cannot be a month, then this row is pasted as it is (actually it is what I need). Is there any way to paste whatever as they are, without any "smart date conversion"? Do I have to change settings in Numberers or Mac OS's System preference?

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  • operator overloading of stream extraction operator in C++ help

    - by Crystal
    I'm having some trouble overloading my stream extraction operator in C++ for a hw assignment. I'm not really sure why I am getting these compile errors since I thought I was doing it right... Here is my code: Complex.h #ifndef COMPLEX_H #define COMPLEX_H class Complex { //friend ostream &operator<<(ostream &output, const Complex &complexObj) const; public: Complex(double = 0.0, double = 0.0); // constructor Complex operator+(const Complex &) const; // addition Complex operator-(const Complex &) const; // subtraction void print() const; // output private: double real; // real part double imaginary; // imaginary part }; #endif Complex.cpp #include <iostream> #include "Complex.h" using namespace std; // Constructor Complex::Complex(double realPart, double imaginaryPart) : real(realPart), imaginary(imaginaryPart) { } // addition operator Complex Complex::operator+(const Complex &operand2) const { return Complex(real + operand2.real, imaginary + operand2.imaginary); } // subtraction operator Complex Complex::operator-(const Complex &operand2) const { return Complex(real - operand2.real, imaginary - operand2.imaginary); } // Overload << operator ostream &Complex::operator<<(ostream &output, const Complex &complexObj) const { cout << '(' << complexObj.real << ", " << complexObj.imaginary << ')'; return output; // returning output allows chaining } // display a Complex object in the form: (a, b) void Complex::print() const { cout << '(' << real << ", " << imaginary << ')'; } main.cpp #include <iostream> #include "Complex.h" using namespace std; int main() { Complex x; Complex y(4.3, 8.2); Complex z(3.3, 1.1); cout << "x: "; x.print(); cout << "\ny: "; y.print(); cout << "\nz: "; z.print(); x = y + z; cout << "\n\nx = y + z: " << endl; x.print(); cout << " = "; y.print(); cout << " + "; z.print(); x = y - z; cout << "\n\nx = y - z: " << endl; x.print(); cout << " = "; y.print(); cout << " - "; z.print(); cout << endl; } Compile erros: complex.cpp(23) : error C2039: '<<' : is not a member of 'Complex' complex.h(5) : see declaration of 'Complex' complex.cpp(24) : error C2270: '<<' : modifiers not allowed on nonmember functions complex.cpp(25) : error C2248: 'Complex::real' : cannot access private member declared in class 'Complex' complex.h(13) : see declaration of 'Complex::real' complex.h(5) : see declaration of 'Complex' complex.cpp(25) : error C2248: 'Complex::imaginary' : cannot access private member declared in class 'Complex' complex.h(14) : see declaration of 'Complex::imaginary' complex.h(5) : see declaration of 'Complex' Thanks!

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  • value types in the vm

    - by john.rose
    value types in the vm p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times} p.p2 {margin: 0.0px 0.0px 14.0px 0.0px; font: 14.0px Times} p.p3 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times} p.p4 {margin: 0.0px 0.0px 15.0px 0.0px; font: 14.0px Times} p.p5 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Courier} p.p6 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Courier; min-height: 17.0px} p.p7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times; min-height: 18.0px} p.p8 {margin: 0.0px 0.0px 0.0px 36.0px; text-indent: -36.0px; font: 14.0px Times; min-height: 18.0px} p.p9 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times; min-height: 18.0px} p.p10 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times; color: #000000} li.li1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times} li.li7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times; min-height: 18.0px} span.s1 {font: 14.0px Courier} span.s2 {color: #000000} span.s3 {font: 14.0px Courier; color: #000000} ol.ol1 {list-style-type: decimal} Or, enduring values for a changing world. Introduction A value type is a data type which, generally speaking, is designed for being passed by value in and out of methods, and stored by value in data structures. The only value types which the Java language directly supports are the eight primitive types. Java indirectly and approximately supports value types, if they are implemented in terms of classes. For example, both Integer and String may be viewed as value types, especially if their usage is restricted to avoid operations appropriate to Object. In this note, we propose a definition of value types in terms of a design pattern for Java classes, accompanied by a set of usage restrictions. We also sketch the relation of such value types to tuple types (which are a JVM-level notion), and point out JVM optimizations that can apply to value types. This note is a thought experiment to extend the JVM’s performance model in support of value types. The demonstration has two phases.  Initially the extension can simply use design patterns, within the current bytecode architecture, and in today’s Java language. But if the performance model is to be realized in practice, it will probably require new JVM bytecode features, changes to the Java language, or both.  We will look at a few possibilities for these new features. An Axiom of Value In the context of the JVM, a value type is a data type equipped with construction, assignment, and equality operations, and a set of typed components, such that, whenever two variables of the value type produce equal corresponding values for their components, the values of the two variables cannot be distinguished by any JVM operation. Here are some corollaries: A value type is immutable, since otherwise a copy could be constructed and the original could be modified in one of its components, allowing the copies to be distinguished. Changing the component of a value type requires construction of a new value. The equals and hashCode operations are strictly component-wise. If a value type is represented by a JVM reference, that reference cannot be successfully synchronized on, and cannot be usefully compared for reference equality. A value type can be viewed in terms of what it doesn’t do. We can say that a value type omits all value-unsafe operations, which could violate the constraints on value types.  These operations, which are ordinarily allowed for Java object types, are pointer equality comparison (the acmp instruction), synchronization (the monitor instructions), all the wait and notify methods of class Object, and non-trivial finalize methods. The clone method is also value-unsafe, although for value types it could be treated as the identity function. Finally, and most importantly, any side effect on an object (however visible) also counts as an value-unsafe operation. A value type may have methods, but such methods must not change the components of the value. It is reasonable and useful to define methods like toString, equals, and hashCode on value types, and also methods which are specifically valuable to users of the value type. Representations of Value Value types have two natural representations in the JVM, unboxed and boxed. An unboxed value consists of the components, as simple variables. For example, the complex number x=(1+2i), in rectangular coordinate form, may be represented in unboxed form by the following pair of variables: /*Complex x = Complex.valueOf(1.0, 2.0):*/ double x_re = 1.0, x_im = 2.0; These variables might be locals, parameters, or fields. Their association as components of a single value is not defined to the JVM. Here is a sample computation which computes the norm of the difference between two complex numbers: double distance(/*Complex x:*/ double x_re, double x_im,         /*Complex y:*/ double y_re, double y_im) {     /*Complex z = x.minus(y):*/     double z_re = x_re - y_re, z_im = x_im - y_im;     /*return z.abs():*/     return Math.sqrt(z_re*z_re + z_im*z_im); } A boxed representation groups component values under a single object reference. The reference is to a ‘wrapper class’ that carries the component values in its fields. (A primitive type can naturally be equated with a trivial value type with just one component of that type. In that view, the wrapper class Integer can serve as a boxed representation of value type int.) The unboxed representation of complex numbers is practical for many uses, but it fails to cover several major use cases: return values, array elements, and generic APIs. The two components of a complex number cannot be directly returned from a Java function, since Java does not support multiple return values. The same story applies to array elements: Java has no ’array of structs’ feature. (Double-length arrays are a possible workaround for complex numbers, but not for value types with heterogeneous components.) By generic APIs I mean both those which use generic types, like Arrays.asList and those which have special case support for primitive types, like String.valueOf and PrintStream.println. Those APIs do not support unboxed values, and offer some problems to boxed values. Any ’real’ JVM type should have a story for returns, arrays, and API interoperability. The basic problem here is that value types fall between primitive types and object types. Value types are clearly more complex than primitive types, and object types are slightly too complicated. Objects are a little bit dangerous to use as value carriers, since object references can be compared for pointer equality, and can be synchronized on. Also, as many Java programmers have observed, there is often a performance cost to using wrapper objects, even on modern JVMs. Even so, wrapper classes are a good starting point for talking about value types. If there were a set of structural rules and restrictions which would prevent value-unsafe operations on value types, wrapper classes would provide a good notation for defining value types. This note attempts to define such rules and restrictions. Let’s Start Coding Now it is time to look at some real code. Here is a definition, written in Java, of a complex number value type. @ValueSafe public final class Complex implements java.io.Serializable {     // immutable component structure:     public final double re, im;     private Complex(double re, double im) {         this.re = re; this.im = im;     }     // interoperability methods:     public String toString() { return "Complex("+re+","+im+")"; }     public List<Double> asList() { return Arrays.asList(re, im); }     public boolean equals(Complex c) {         return re == c.re && im == c.im;     }     public boolean equals(@ValueSafe Object x) {         return x instanceof Complex && equals((Complex) x);     }     public int hashCode() {         return 31*Double.valueOf(re).hashCode()                 + Double.valueOf(im).hashCode();     }     // factory methods:     public static Complex valueOf(double re, double im) {         return new Complex(re, im);     }     public Complex changeRe(double re2) { return valueOf(re2, im); }     public Complex changeIm(double im2) { return valueOf(re, im2); }     public static Complex cast(@ValueSafe Object x) {         return x == null ? ZERO : (Complex) x;     }     // utility methods and constants:     public Complex plus(Complex c)  { return new Complex(re+c.re, im+c.im); }     public Complex minus(Complex c) { return new Complex(re-c.re, im-c.im); }     public double abs() { return Math.sqrt(re*re + im*im); }     public static final Complex PI = valueOf(Math.PI, 0.0);     public static final Complex ZERO = valueOf(0.0, 0.0); } This is not a minimal definition, because it includes some utility methods and other optional parts.  The essential elements are as follows: The class is marked as a value type with an annotation. The class is final, because it does not make sense to create subclasses of value types. The fields of the class are all non-private and final.  (I.e., the type is immutable and structurally transparent.) From the supertype Object, all public non-final methods are overridden. The constructor is private. Beyond these bare essentials, we can observe the following features in this example, which are likely to be typical of all value types: One or more factory methods are responsible for value creation, including a component-wise valueOf method. There are utility methods for complex arithmetic and instance creation, such as plus and changeIm. There are static utility constants, such as PI. The type is serializable, using the default mechanisms. There are methods for converting to and from dynamically typed references, such as asList and cast. The Rules In order to use value types properly, the programmer must avoid value-unsafe operations.  A helpful Java compiler should issue errors (or at least warnings) for code which provably applies value-unsafe operations, and should issue warnings for code which might be correct but does not provably avoid value-unsafe operations.  No such compilers exist today, but to simplify our account here, we will pretend that they do exist. A value-safe type is any class, interface, or type parameter marked with the @ValueSafe annotation, or any subtype of a value-safe type.  If a value-safe class is marked final, it is in fact a value type.  All other value-safe classes must be abstract.  The non-static fields of a value class must be non-public and final, and all its constructors must be private. Under the above rules, a standard interface could be helpful to define value types like Complex.  Here is an example: @ValueSafe public interface ValueType extends java.io.Serializable {     // All methods listed here must get redefined.     // Definitions must be value-safe, which means     // they may depend on component values only.     List<? extends Object> asList();     int hashCode();     boolean equals(@ValueSafe Object c);     String toString(); } //@ValueSafe inherited from supertype: public final class Complex implements ValueType { … The main advantage of such a conventional interface is that (unlike an annotation) it is reified in the runtime type system.  It could appear as an element type or parameter bound, for facilities which are designed to work on value types only.  More broadly, it might assist the JVM to perform dynamic enforcement of the rules for value types. Besides types, the annotation @ValueSafe can mark fields, parameters, local variables, and methods.  (This is redundant when the type is also value-safe, but may be useful when the type is Object or another supertype of a value type.)  Working forward from these annotations, an expression E is defined as value-safe if it satisfies one or more of the following: The type of E is a value-safe type. E names a field, parameter, or local variable whose declaration is marked @ValueSafe. E is a call to a method whose declaration is marked @ValueSafe. E is an assignment to a value-safe variable, field reference, or array reference. E is a cast to a value-safe type from a value-safe expression. E is a conditional expression E0 ? E1 : E2, and both E1 and E2 are value-safe. Assignments to value-safe expressions and initializations of value-safe names must take their values from value-safe expressions. A value-safe expression may not be the subject of a value-unsafe operation.  In particular, it cannot be synchronized on, nor can it be compared with the “==” operator, not even with a null or with another value-safe type. In a program where all of these rules are followed, no value-type value will be subject to a value-unsafe operation.  Thus, the prime axiom of value types will be satisfied, that no two value type will be distinguishable as long as their component values are equal. More Code To illustrate these rules, here are some usage examples for Complex: Complex pi = Complex.valueOf(Math.PI, 0); Complex zero = pi.changeRe(0);  //zero = pi; zero.re = 0; ValueType vtype = pi; @SuppressWarnings("value-unsafe")   Object obj = pi; @ValueSafe Object obj2 = pi; obj2 = new Object();  // ok List<Complex> clist = new ArrayList<Complex>(); clist.add(pi);  // (ok assuming List.add param is @ValueSafe) List<ValueType> vlist = new ArrayList<ValueType>(); vlist.add(pi);  // (ok) List<Object> olist = new ArrayList<Object>(); olist.add(pi);  // warning: "value-unsafe" boolean z = pi.equals(zero); boolean z1 = (pi == zero);  // error: reference comparison on value type boolean z2 = (pi == null);  // error: reference comparison on value type boolean z3 = (pi == obj2);  // error: reference comparison on value type synchronized (pi) { }  // error: synch of value, unpredictable result synchronized (obj2) { }  // unpredictable result Complex qq = pi; qq = null;  // possible NPE; warning: “null-unsafe" qq = (Complex) obj;  // warning: “null-unsafe" qq = Complex.cast(obj);  // OK @SuppressWarnings("null-unsafe")   Complex empty = null;  // possible NPE qq = empty;  // possible NPE (null pollution) The Payoffs It follows from this that either the JVM or the java compiler can replace boxed value-type values with unboxed ones, without affecting normal computations.  Fields and variables of value types can be split into their unboxed components.  Non-static methods on value types can be transformed into static methods which take the components as value parameters. Some common questions arise around this point in any discussion of value types. Why burden the programmer with all these extra rules?  Why not detect programs automagically and perform unboxing transparently?  The answer is that it is easy to break the rules accidently unless they are agreed to by the programmer and enforced.  Automatic unboxing optimizations are tantalizing but (so far) unreachable ideal.  In the current state of the art, it is possible exhibit benchmarks in which automatic unboxing provides the desired effects, but it is not possible to provide a JVM with a performance model that assures the programmer when unboxing will occur.  This is why I’m writing this note, to enlist help from, and provide assurances to, the programmer.  Basically, I’m shooting for a good set of user-supplied “pragmas” to frame the desired optimization. Again, the important thing is that the unboxing must be done reliably, or else programmers will have no reason to work with the extra complexity of the value-safety rules.  There must be a reasonably stable performance model, wherein using a value type has approximately the same performance characteristics as writing the unboxed components as separate Java variables. There are some rough corners to the present scheme.  Since Java fields and array elements are initialized to null, value-type computations which incorporate uninitialized variables can produce null pointer exceptions.  One workaround for this is to require such variables to be null-tested, and the result replaced with a suitable all-zero value of the value type.  That is what the “cast” method does above. Generically typed APIs like List<T> will continue to manipulate boxed values always, at least until we figure out how to do reification of generic type instances.  Use of such APIs will elicit warnings until their type parameters (and/or relevant members) are annotated or typed as value-safe.  Retrofitting List<T> is likely to expose flaws in the present scheme, which we will need to engineer around.  Here are a couple of first approaches: public interface java.util.List<@ValueSafe T> extends Collection<T> { … public interface java.util.List<T extends Object|ValueType> extends Collection<T> { … (The second approach would require disjunctive types, in which value-safety is “contagious” from the constituent types.) With more transformations, the return value types of methods can also be unboxed.  This may require significant bytecode-level transformations, and would work best in the presence of a bytecode representation for multiple value groups, which I have proposed elsewhere under the title “Tuples in the VM”. But for starters, the JVM can apply this transformation under the covers, to internally compiled methods.  This would give a way to express multiple return values and structured return values, which is a significant pain-point for Java programmers, especially those who work with low-level structure types favored by modern vector and graphics processors.  The lack of multiple return values has a strong distorting effect on many Java APIs. Even if the JVM fails to unbox a value, there is still potential benefit to the value type.  Clustered computing systems something have copy operations (serialization or something similar) which apply implicitly to command operands.  When copying JVM objects, it is extremely helpful to know when an object’s identity is important or not.  If an object reference is a copied operand, the system may have to create a proxy handle which points back to the original object, so that side effects are visible.  Proxies must be managed carefully, and this can be expensive.  On the other hand, value types are exactly those types which a JVM can “copy and forget” with no downside. Array types are crucial to bulk data interfaces.  (As data sizes and rates increase, bulk data becomes more important than scalar data, so arrays are definitely accompanying us into the future of computing.)  Value types are very helpful for adding structure to bulk data, so a successful value type mechanism will make it easier for us to express richer forms of bulk data. Unboxing arrays (i.e., arrays containing unboxed values) will provide better cache and memory density, and more direct data movement within clustered or heterogeneous computing systems.  They require the deepest transformations, relative to today’s JVM.  There is an impedance mismatch between value-type arrays and Java’s covariant array typing, so compromises will need to be struck with existing Java semantics.  It is probably worth the effort, since arrays of unboxed value types are inherently more memory-efficient than standard Java arrays, which rely on dependent pointer chains. It may be sufficient to extend the “value-safe” concept to array declarations, and allow low-level transformations to change value-safe array declarations from the standard boxed form into an unboxed tuple-based form.  Such value-safe arrays would not be convertible to Object[] arrays.  Certain connection points, such as Arrays.copyOf and System.arraycopy might need additional input/output combinations, to allow smooth conversion between arrays with boxed and unboxed elements. Alternatively, the correct solution may have to wait until we have enough reification of generic types, and enough operator overloading, to enable an overhaul of Java arrays. Implicit Method Definitions The example of class Complex above may be unattractively complex.  I believe most or all of the elements of the example class are required by the logic of value types. If this is true, a programmer who writes a value type will have to write lots of error-prone boilerplate code.  On the other hand, I think nearly all of the code (except for the domain-specific parts like plus and minus) can be implicitly generated. Java has a rule for implicitly defining a class’s constructor, if no it defines no constructors explicitly.  Likewise, there are rules for providing default access modifiers for interface members.  Because of the highly regular structure of value types, it might be reasonable to perform similar implicit transformations on value types.  Here’s an example of a “highly implicit” definition of a complex number type: public class Complex implements ValueType {  // implicitly final     public double re, im;  // implicitly public final     //implicit methods are defined elementwise from te fields:     //  toString, asList, equals(2), hashCode, valueOf, cast     //optionally, explicit methods (plus, abs, etc.) would go here } In other words, with the right defaults, a simple value type definition can be a one-liner.  The observant reader will have noticed the similarities (and suitable differences) between the explicit methods above and the corresponding methods for List<T>. Another way to abbreviate such a class would be to make an annotation the primary trigger of the functionality, and to add the interface(s) implicitly: public @ValueType class Complex { … // implicitly final, implements ValueType (But to me it seems better to communicate the “magic” via an interface, even if it is rooted in an annotation.) Implicitly Defined Value Types So far we have been working with nominal value types, which is to say that the sequence of typed components is associated with a name and additional methods that convey the intention of the programmer.  A simple ordered pair of floating point numbers can be variously interpreted as (to name a few possibilities) a rectangular or polar complex number or Cartesian point.  The name and the methods convey the intended meaning. But what if we need a truly simple ordered pair of floating point numbers, without any further conceptual baggage?  Perhaps we are writing a method (like “divideAndRemainder”) which naturally returns a pair of numbers instead of a single number.  Wrapping the pair of numbers in a nominal type (like “QuotientAndRemainder”) makes as little sense as wrapping a single return value in a nominal type (like “Quotient”).  What we need here are structural value types commonly known as tuples. For the present discussion, let us assign a conventional, JVM-friendly name to tuples, roughly as follows: public class java.lang.tuple.$DD extends java.lang.tuple.Tuple {      double $1, $2; } Here the component names are fixed and all the required methods are defined implicitly.  The supertype is an abstract class which has suitable shared declarations.  The name itself mentions a JVM-style method parameter descriptor, which may be “cracked” to determine the number and types of the component fields. The odd thing about such a tuple type (and structural types in general) is it must be instantiated lazily, in response to linkage requests from one or more classes that need it.  The JVM and/or its class loaders must be prepared to spin a tuple type on demand, given a simple name reference, $xyz, where the xyz is cracked into a series of component types.  (Specifics of naming and name mangling need some tasteful engineering.) Tuples also seem to demand, even more than nominal types, some support from the language.  (This is probably because notations for non-nominal types work best as combinations of punctuation and type names, rather than named constructors like Function3 or Tuple2.)  At a minimum, languages with tuples usually (I think) have some sort of simple bracket notation for creating tuples, and a corresponding pattern-matching syntax (or “destructuring bind”) for taking tuples apart, at least when they are parameter lists.  Designing such a syntax is no simple thing, because it ought to play well with nominal value types, and also with pre-existing Java features, such as method parameter lists, implicit conversions, generic types, and reflection.  That is a task for another day. Other Use Cases Besides complex numbers and simple tuples there are many use cases for value types.  Many tuple-like types have natural value-type representations. These include rational numbers, point locations and pixel colors, and various kinds of dates and addresses. Other types have a variable-length ‘tail’ of internal values. The most common example of this is String, which is (mathematically) a sequence of UTF-16 character values. Similarly, bit vectors, multiple-precision numbers, and polynomials are composed of sequences of values. Such types include, in their representation, a reference to a variable-sized data structure (often an array) which (somehow) represents the sequence of values. The value type may also include ’header’ information. Variable-sized values often have a length distribution which favors short lengths. In that case, the design of the value type can make the first few values in the sequence be direct ’header’ fields of the value type. In the common case where the header is enough to represent the whole value, the tail can be a shared null value, or even just a null reference. Note that the tail need not be an immutable object, as long as the header type encapsulates it well enough. This is the case with String, where the tail is a mutable (but never mutated) character array. Field types and their order must be a globally visible part of the API.  The structure of the value type must be transparent enough to have a globally consistent unboxed representation, so that all callers and callees agree about the type and order of components  that appear as parameters, return types, and array elements.  This is a trade-off between efficiency and encapsulation, which is forced on us when we remove an indirection enjoyed by boxed representations.  A JVM-only transformation would not care about such visibility, but a bytecode transformation would need to take care that (say) the components of complex numbers would not get swapped after a redefinition of Complex and a partial recompile.  Perhaps constant pool references to value types need to declare the field order as assumed by each API user. This brings up the delicate status of private fields in a value type.  It must always be possible to load, store, and copy value types as coordinated groups, and the JVM performs those movements by moving individual scalar values between locals and stack.  If a component field is not public, what is to prevent hostile code from plucking it out of the tuple using a rogue aload or astore instruction?  Nothing but the verifier, so we may need to give it more smarts, so that it treats value types as inseparable groups of stack slots or locals (something like long or double). My initial thought was to make the fields always public, which would make the security problem moot.  But public is not always the right answer; consider the case of String, where the underlying mutable character array must be encapsulated to prevent security holes.  I believe we can win back both sides of the tradeoff, by training the verifier never to split up the components in an unboxed value.  Just as the verifier encapsulates the two halves of a 64-bit primitive, it can encapsulate the the header and body of an unboxed String, so that no code other than that of class String itself can take apart the values. Similar to String, we could build an efficient multi-precision decimal type along these lines: public final class DecimalValue extends ValueType {     protected final long header;     protected private final BigInteger digits;     public DecimalValue valueOf(int value, int scale) {         assert(scale >= 0);         return new DecimalValue(((long)value << 32) + scale, null);     }     public DecimalValue valueOf(long value, int scale) {         if (value == (int) value)             return valueOf((int)value, scale);         return new DecimalValue(-scale, new BigInteger(value));     } } Values of this type would be passed between methods as two machine words. Small values (those with a significand which fits into 32 bits) would be represented without any heap data at all, unless the DecimalValue itself were boxed. (Note the tension between encapsulation and unboxing in this case.  It would be better if the header and digits fields were private, but depending on where the unboxing information must “leak”, it is probably safer to make a public revelation of the internal structure.) Note that, although an array of Complex can be faked with a double-length array of double, there is no easy way to fake an array of unboxed DecimalValues.  (Either an array of boxed values or a transposed pair of homogeneous arrays would be reasonable fallbacks, in a current JVM.)  Getting the full benefit of unboxing and arrays will require some new JVM magic. Although the JVM emphasizes portability, system dependent code will benefit from using machine-level types larger than 64 bits.  For example, the back end of a linear algebra package might benefit from value types like Float4 which map to stock vector types.  This is probably only worthwhile if the unboxing arrays can be packed with such values. More Daydreams A more finely-divided design for dynamic enforcement of value safety could feature separate marker interfaces for each invariant.  An empty marker interface Unsynchronizable could cause suitable exceptions for monitor instructions on objects in marked classes.  More radically, a Interchangeable marker interface could cause JVM primitives that are sensitive to object identity to raise exceptions; the strangest result would be that the acmp instruction would have to be specified as raising an exception. @ValueSafe public interface ValueType extends java.io.Serializable,         Unsynchronizable, Interchangeable { … public class Complex implements ValueType {     // inherits Serializable, Unsynchronizable, Interchangeable, @ValueSafe     … It seems possible that Integer and the other wrapper types could be retro-fitted as value-safe types.  This is a major change, since wrapper objects would be unsynchronizable and their references interchangeable.  It is likely that code which violates value-safety for wrapper types exists but is uncommon.  It is less plausible to retro-fit String, since the prominent operation String.intern is often used with value-unsafe code. We should also reconsider the distinction between boxed and unboxed values in code.  The design presented above obscures that distinction.  As another thought experiment, we could imagine making a first class distinction in the type system between boxed and unboxed representations.  Since only primitive types are named with a lower-case initial letter, we could define that the capitalized version of a value type name always refers to the boxed representation, while the initial lower-case variant always refers to boxed.  For example: complex pi = complex.valueOf(Math.PI, 0); Complex boxPi = pi;  // convert to boxed myList.add(boxPi); complex z = myList.get(0);  // unbox Such a convention could perhaps absorb the current difference between int and Integer, double and Double. It might also allow the programmer to express a helpful distinction among array types. As said above, array types are crucial to bulk data interfaces, but are limited in the JVM.  Extending arrays beyond the present limitations is worth thinking about; for example, the Maxine JVM implementation has a hybrid object/array type.  Something like this which can also accommodate value type components seems worthwhile.  On the other hand, does it make sense for value types to contain short arrays?  And why should random-access arrays be the end of our design process, when bulk data is often sequentially accessed, and it might make sense to have heterogeneous streams of data as the natural “jumbo” data structure.  These considerations must wait for another day and another note. More Work It seems to me that a good sequence for introducing such value types would be as follows: Add the value-safety restrictions to an experimental version of javac. Code some sample applications with value types, including Complex and DecimalValue. Create an experimental JVM which internally unboxes value types but does not require new bytecodes to do so.  Ensure the feasibility of the performance model for the sample applications. Add tuple-like bytecodes (with or without generic type reification) to a major revision of the JVM, and teach the Java compiler to switch in the new bytecodes without code changes. A staggered roll-out like this would decouple language changes from bytecode changes, which is always a convenient thing. A similar investigation should be applied (concurrently) to array types.  In this case, it seems to me that the starting point is in the JVM: Add an experimental unboxing array data structure to a production JVM, perhaps along the lines of Maxine hybrids.  No bytecode or language support is required at first; everything can be done with encapsulated unsafe operations and/or method handles. Create an experimental JVM which internally unboxes value types but does not require new bytecodes to do so.  Ensure the feasibility of the performance model for the sample applications. Add tuple-like bytecodes (with or without generic type reification) to a major revision of the JVM, and teach the Java compiler to switch in the new bytecodes without code changes. That’s enough musing me for now.  Back to work!

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  • Entity Association Mapping with Code First Part 1 : Mapping Complex Types

    - by mortezam
    Last week the CTP5 build of the new Entity Framework Code First has been released by data team at Microsoft. Entity Framework Code-First provides a pretty powerful code-centric way to work with the databases. When it comes to associations, it brings ultimate flexibility. I’m a big fan of the EF Code First approach and am planning to explain association mapping with code first in a series of blog posts and this one is dedicated to Complex Types. If you are new to Code First approach, you can find a great walkthrough here. In order to build a solid foundation for our discussion, we will start by learning about some of the core concepts around the relationship mapping.   What is Mapping?Mapping is the act of determining how objects and their relationships are persisted in permanent data storage, in our case, relational databases. What is Relationship mapping?A mapping that describes how to persist a relationship (association, aggregation, or composition) between two or more objects. Types of RelationshipsThere are two categories of object relationships that we need to be concerned with when mapping associations. The first category is based on multiplicity and it includes three types: One-to-one relationships: This is a relationship where the maximums of each of its multiplicities is one. One-to-many relationships: Also known as a many-to-one relationship, this occurs when the maximum of one multiplicity is one and the other is greater than one. Many-to-many relationships: This is a relationship where the maximum of both multiplicities is greater than one. The second category is based on directionality and it contains two types: Uni-directional relationships: when an object knows about the object(s) it is related to but the other object(s) do not know of the original object. To put this in EF terminology, when a navigation property exists only on one of the association ends and not on the both. Bi-directional relationships: When the objects on both end of the relationship know of each other (i.e. a navigation property defined on both ends). How Object Relationships Are Implemented in POCO domain models?When the multiplicity is one (e.g. 0..1 or 1) the relationship is implemented by defining a navigation property that reference the other object (e.g. an Address property on User class). When the multiplicity is many (e.g. 0..*, 1..*) the relationship is implemented via an ICollection of the type of other object. How Relational Database Relationships Are Implemented? Relationships in relational databases are maintained through the use of Foreign Keys. A foreign key is a data attribute(s) that appears in one table and must be the primary key or other candidate key in another table. With a one-to-one relationship the foreign key needs to be implemented by one of the tables. To implement a one-to-many relationship we implement a foreign key from the “one table” to the “many table”. We could also choose to implement a one-to-many relationship via an associative table (aka Join table), effectively making it a many-to-many relationship. Introducing the ModelNow, let's review the model that we are going to use in order to implement Complex Type with Code First. It's a simple object model which consist of two classes: User and Address. Each user could have one billing address. The Address information of a User is modeled as a separate class as you can see in the UML model below: In object-modeling terms, this association is a kind of aggregation—a part-of relationship. Aggregation is a strong form of association; it has some additional semantics with regard to the lifecycle of objects. In this case, we have an even stronger form, composition, where the lifecycle of the part is fully dependent upon the lifecycle of the whole. Fine-grained domain models The motivation behind this design was to achieve Fine-grained domain models. In crude terms, fine-grained means “more classes than tables”. For example, a user may have both a billing address and a home address. In the database, you may have a single User table with the columns BillingStreet, BillingCity, and BillingPostalCode along with HomeStreet, HomeCity, and HomePostalCode. There are good reasons to use this somewhat denormalized relational model (performance, for one). In our object model, we can use the same approach, representing the two addresses as six string-valued properties of the User class. But it’s much better to model this using an Address class, where User has the BillingAddress and HomeAddress properties. This object model achieves improved cohesion and greater code reuse and is more understandable. Complex Types: Splitting a Table Across Multiple Types Back to our model, there is no difference between this composition and other weaker styles of association when it comes to the actual C# implementation. But in the context of ORM, there is a big difference: A composed class is often a candidate Complex Type. But C# has no concept of composition—a class or property can’t be marked as a composition. The only difference is the object identifier: a complex type has no individual identity (i.e. no AddressId defined on Address class) which make sense because when it comes to the database everything is going to be saved into one single table. How to implement a Complex Types with Code First Code First has a concept of Complex Type Discovery that works based on a set of Conventions. The convention is that if Code First discovers a class where a primary key cannot be inferred, and no primary key is registered through Data Annotations or the fluent API, then the type will be automatically registered as a complex type. Complex type detection also requires that the type does not have properties that reference entity types (i.e. all the properties must be scalar types) and is not referenced from a collection property on another type. Here is the implementation: public class User{    public int UserId { get; set; }    public string FirstName { get; set; }    public string LastName { get; set; }    public string Username { get; set; }    public Address Address { get; set; }} public class Address {     public string Street { get; set; }     public string City { get; set; }            public string PostalCode { get; set; }        }public class EntityMappingContext : DbContext {     public DbSet<User> Users { get; set; }        } With code first, this is all of the code we need to write to create a complex type, we do not need to configure any additional database schema mapping information through Data Annotations or the fluent API. Database SchemaThe mapping result for this object model is as follows: Limitations of this mappingThere are two important limitations to classes mapped as Complex Types: Shared references is not possible: The Address Complex Type doesn’t have its own database identity (primary key) and so can’t be referred to by any object other than the containing instance of User (e.g. a Shipping class that also needs to reference the same User Address). No elegant way to represent a null reference There is no elegant way to represent a null reference to an Address. When reading from database, EF Code First always initialize Address object even if values in all mapped columns of the complex type are null. This means that if you store a complex type object with all null property values, EF Code First returns a initialized complex type when the owning entity object is retrieved from the database. SummaryIn this post we learned about fine-grained domain models which complex type is just one example of it. Fine-grained is fully supported by EF Code First and is known as the most important requirement for a rich domain model. Complex type is usually the simplest way to represent one-to-one relationships and because the lifecycle is almost always dependent in such a case, it’s either an aggregation or a composition in UML. In the next posts we will revisit the same domain model and will learn about other ways to map a one-to-one association that does not have the limitations of the complex types. References ADO.NET team blog Mapping Objects to Relational Databases Java Persistence with Hibernate

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  • fluent api complex example

    - by intern
    we have tried some of simple Fluent API examples. to brush up our skills we want to move ahead to complex examples. but we do not what to make as a complex fluent api. can anyone suggest what should we make or where can we get the idea about it? we have recently started writing fluent api codes in Ruby and have tested very basic ones. Now we want to move to complex ones to get better idea about it.

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  • PHP detmine numbers in between two numbers then query

    - by Joshua Anderson
    This should be simple but I can't figure it out <?php $testid = 240; $curid = 251; $cal = $curid - $testid; echo $cal; ?> I want to determine the numbers in between two other numbers so for this example it detects there are 11 numbers in between the $testid and $curid, but i dont need it to do that. I need it to literally figure the numbers in between $curid - $testid which in this example would be 241, 242, 243... all the way to 251 then i need to create a loop with those numbers and do a query below with each one $cal = $curid - $testid; mysql_query("SELECT * FROM wall WHERE id='".$cal."'") // and for each number mysql should out put each data field with those numbers. Thanks again, love you guys.

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  • Paste string of date format mm/dd/yy to iWork-Numbers

    - by David.Chu.ca
    I have trouble to paste a list of strings in the format of 'mm/dd/yy' into iWork-Numbers. For example: 04/01/10 04/03/10 04/13/10 The result will be: 2004-01-10 2004-03-10 04/13/10 It looks like that Numbers convert the mm into year, then month and last day. Is there any way to paste whatever as they are? Do I have to change settings in Numberers or System preference?

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