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  • Are there programming languages that allow you to do set arithmetic on types?

    - by Will Brown
    Out of curiosity, are there languages that allow you to do set arithmetic on types to create new types? Something like: interface A { void a(); void b(); } interface B { void b(); void c(); } interface C = A & B; // has b() interface D = A | B; // has a(), b() and c() interface E = (A & B) ^ B; // has c() I know that in some languages these ideas can be expressed (i.e., Java has List<Comparable & Serializable> for the union of the interfaces) but I've never heard of a language that supports type arithmetic. Thanks!

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  • Need alternative to Accessibility's "Locate Pointer" to visually highlight the mouse.

    - by fred.bear
    Update: See end of quetion: A black-on-white cross-hair/I-bar mouse-pointer is soemtimes hard foe me to spot in amongst black-on-white text. I've tried "Accessibility / Mouse Accessibility / Locate Pointer" .. which will: Show pointer position when Control is presssed It works (to a point), but it does have a notable problem, which renders it inpractical. It has the uncanny side-effect of disallowing all Control key navigation while editing a file/dir name in Nautilus (F2).. Just touching the Control key drops it out of edit mode, which means I can't keyboard paste, move-L/R word etc... So, I'm looking for an alternative. I've tried Compiz's Water Effect, but I need something which is sharper, faster, and localized to the pointer. Compiz's Show Mouse (with fire) is no suitable. I'm really lookingf for an analog of "Accessibility / Locate Pointer": * ie. I hit Control (only).. and it blips a quick visual pulse. UPDATE: I've just realized why I can't find my mouse so often! ... It's because it is isn't there !!! ... Two apps I use a lot, Gedit and Konsole (KDE Terminal; it renders unicode better), ... dissolve the mouse-pointer to invisible after the first key is typed ... and Konsole does it after a few seconds of idle-time... like a video-player option: "hide the mouse".. Well I don't use the mouse much, and I thought it was juse my eyesight (which does rely a lot on Compiz's zoom)... I discovered it when I installed a "novelty" app, called Geyes from gnome-applets ("A goofy set of eyes for the GNOME panel. They follow your mouse.") ... It could follow the mouse better than me! :)

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  • Tech Article: Tired of Null Pointer Exceptions? Use Java SE 8's Optional!

    - by Tori Wieldt
    A wise man once said you are not a real Java programmer until you've dealt with a null pointer exception. The null reference is the source of many problems because it is often used to denote the absence of a value. Java SE 8 introduces a new class called java.util.Optional that can alleviate some of these problems. In the tech article "Tired of Null Pointer Exceptions? Use Java SE 8's Optional!" Java expert Raoul-Gabriel Urma shows you how to make your code more readable and protect it against null pointer exceptions. Urma explains "The purpose of Optional is not to replace every single null reference in your codebase but rather to help design better APIs in which—just by reading the signature of a method—users can tell whether to expect an optional value. In addition, Optional forces you to actively unwrap an Optional to deal with the absence of a value; as a result, you protect your code against unintended null pointer exceptions." Learn how to go from writing painful nested null checks to writing declarative code that is composable, readable, and better protected from null pointer exceptions. Read "Tired of Null Pointer Exceptions? Use Java SE 8's Optional!"

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  • PHP bitwise left shifting 32 spaces problem and bad results with large numbers arithmetic operations

    - by Victor Stanciu
    Hello, I have the following problems: First: I am trying to do a 32-spaces bitwise left shift on a large number, and for some reason the number is always returned as-is. For example: echo(516103988<<32); // echoes 516103988 Because shifting the bits to the left one space is the equivalent of multiplying by 2, i tried multiplying the number by 2^32, and it works, it returns 2216649749795176448. Second: I have to add 9379 to the number from the above point: printf('%0.0f', 2216649749795176448 + 9379); // prints 2216649749795185920 Should print: 2216649749795185827

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  • Converting Oracle date arithmetic to work in HSQLDB

    - by JBristow
    I'm trying to spot-test an Oracle backed database with hsqldb and dbunit, but I've run into a snag. The problem is with the following EJB-QL (simplified a bit): SELECT o FROM Offer o WHERE :nowTime BETWEEN o.startDate AND o.startDate + 7 This seems to only work in Oracle's version of SQL. What's the easiest way for me to convert this to work in both hsqldb and oracle? Assume that changing the two between arguments to named parameters is a very difficult refactor, so I'm going to favor answers that provides a more standardized analog to o.startdate + 7 EDIT: After doing some more research, it looks like Oracle converts the above snippet to o.startdate + INTERVAL '7' DAY which is apparently more standard, but doesn't work in HSQLDB.

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  • Doing 64 bit manipulation using 32 bit data in Fixed point arithmetic using C.

    - by Viks
    Hi, I am stuck with a problem. I am working on a hardware which only does support 32 bit operations. sizeof(int64_t) is 4. Sizeof(int) is 4. and I am porting an application which assumes size of int64_t to be 8 bytes. The problem is it has this macro BIG_MULL(a,b) ( (int64_t)(a) * (int64_t)(b) 23) The result is always a 32 bit integer but since my system doesn't support 64 bit operation, it always return me the LSB of the operation, rounding of all the results making my system crash. Can someone help me out? Regards, Vikas Gupta

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  • Beginner SQL question: arithmetic with multiple COUNT(*) results

    - by polygenelubricants
    Continuing with the spirit of using the Stack Exchange Data Explorer to learn SQL, (see: Can we become our own “Northwind” for teaching SQL / databases?), I've decided to try to write a query to answer a simple question (on meta): What % of stackoverflow users have over 10,000 rep?. Here's what I've done: Query#1 SELECT COUNT(*) FROM Users WHERE Users.Reputation >= 10000 Result: 556 Query#2 SELECT COUNT(*) FROM USERS Result: 227691 Now, how do I put them together into one query? What is this query idiom called? What do I need to write so I can get, say, a one-row three-column result like this: 556 227691 0,00244190592

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  • Date arithmetic using integer values

    - by Dave Jarvis
    Problem String concatenation is slowing down a query: date(extract(YEAR FROM m.taken)||'-1-1') d1, date(extract(YEAR FROM m.taken)||'-1-31') d2 This is realized in code as part of a string, which follows (where the p_ variables are integers): date(extract(YEAR FROM m.taken)||''-'||p_month1||'-'||p_day1||''') d1, date(extract(YEAR FROM m.taken)||''-'||p_month2||'-'||p_day2||''') d2 This part of the query runs in 3.2 seconds with the dates, and 1.5 seconds without, leading me to believe there is ample room for improvement. Question What is a better way to create the date (presumably without concatenation)? Many thanks!

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  • C# Expression Tree Simple Arithmetic

    - by Richard Adnams
    Hello, I've been trying to figure out how to achieve some simple maths using the Expression class. What I'm trying to do is this (1 + 10 * 15) When I try to do this via Expression.Add and Expression.Constant but the result I get is this ((1 + 10) * 15) Which is not right as it evaluates the 1 + 10 first instead of 10 * 15. Is there a way to combine Expression.Add/Multiply etc.. without it creating the brackets? I assume there is but I just can't find where or how! The test code I have is this var v1 = Expression.Constant(1, typeof(int)); var v2 = Expression.Constant(10, typeof(int)); var v3 = Expression.Constant(15, typeof(int)); var a1 = Expression.Add(v1, v2); var m2 = Expression.Multiply(a1, v3); Thanks for your time, Richard.

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  • Problem with JavaScript arithmetic

    - by Lynn
    I have a form for my customers to add budget projections. A prominent user wants to be able to show dollar values in either dollars, Kila-dollars or Mega-dollars. I'm trying to achieve this with a group of radio buttons that call the following JavaScript function, but am having problems with rounding that make the results look pretty crummy. Any advice would be much appreciated! Lynn function setDollars(new_mode) { var factor; var myfield; var myval; var cur_mode = document.proj_form.cur_dollars.value; if(cur_mode == new_mode) { return; } else if((cur_mode == 'd')&&(new_mode == 'kd')) { factor = "0.001"; } else if((cur_mode == 'd')&&(new_mode == 'md')) { factor = "0.000001"; } else if((cur_mode == 'kd')&&(new_mode == 'd')) { factor = "1000"; } else if((cur_mode == 'kd')&&(new_mode == 'md')) { factor = "0.001"; } else if((cur_mode == 'md')&&(new_mode == 'kd')) { factor = "1000"; } else if((cur_mode == 'md')&&(new_mode == 'd')) { factor = "1000000"; } document.proj_form.cur_dollars.value = new_mode; var cur_idx = document.proj_form.cur_idx.value; var available_slots = 13 - cur_idx; var td_name; var cell; var new_value; //Adjust dollar values for projections for(i=1;i<13;i++) { var myfield = eval('document.proj_form.proj_'+i); if(myfield.value == '') { myfield.value = 0; } var myval = parseFloat(myfield.value) * parseFloat(factor); myfield.value = myval; if(i < cur_idx) { document.getElementById("actual_"+i).innerHTML = myval; } }

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  • Floating Point Arithmetic - Modulo Operator on Double Type

    - by CrimsonX
    So I'm trying to figure out why the modulo operator is returning such a large unusual value. If I have the code: double result = 1.0d % 0.1d; it will give a result of 0.09999999999999995. I would expect a value of 0 Note this problem doesn't exist using the dividing operator - double result = 1.0d / 0.1d; will give a result of 10.0, meaning that the remainder should be 0. Let me be clear: I'm not surprised that an error exists, I'm surprised that the error is so darn large compared to the numbers at play. 0.0999 ~= 0.1 and 0.1 is on the same order of magnitude as 0.1d and only one order of magnitude away from 1.0d. Its not like you can compare it to a double.epsilon, or say "its equal if its < 0.00001 difference". I've read up on this topic on StackOverflow, in the following posts one two three, amongst others. Can anyone suggest explain why this error is so large? Any any suggestions to avoid running into the problems in the future (I know I could use decimal instead but I'm concerned about the performance of that).

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  • Generate a list of file names based on month and year arithmetic

    - by MacUsers
    How can I list the numbers 01 to 12 (one for each of the 12 months) in such a way so that the current month always comes last where the oldest one is first. In other words, if the number is grater than the current month, it's from the previous year. e.g. 02 is Feb, 2011 (the current month right now), 03 is March, 2010 and 09 is Sep, 2010 but 01 is Jan, 2011. In this case, I'd like to have [09, 03, 01, 02]. This is what I'm doing to determine the year: for inFile in os.listdir('.'): if inFile.isdigit(): month = months[int(inFile)] if int(inFile) <= int(strftime("%m")): year = strftime("%Y") else: year = int(strftime("%Y"))-1 mnYear = month + ", " + str(year) I don't have a clue what to do next. What should I do here? Update: I think, I better upload the entire script for better understanding. #!/usr/bin/env python import os, sys from time import strftime from calendar import month_abbr vGroup = {} vo = "group_lhcb" SI00_fig = float(2.478) months = tuple(month_abbr) print "\n%-12s\t%10s\t%8s\t%10s" % ('VOs','CPU-time','CPU-time','kSI2K-hrs') print "%-12s\t%10s\t%8s\t%10s" % ('','(in Sec)','(in Hrs)','(*2.478)') print "=" * 58 for inFile in os.listdir('.'): if inFile.isdigit(): readFile = open(inFile, 'r') lines = readFile.readlines() readFile.close() month = months[int(inFile)] if int(inFile) <= int(strftime("%m")): year = strftime("%Y") else: year = int(strftime("%Y"))-1 mnYear = month + ", " + str(year) for line in lines[2:]: if line.find(vo)==0: g, i = line.split() s = vGroup.get(g, 0) vGroup[g] = s + int(i) sumHrs = ((vGroup[g]/60)/60) sumSi2k = sumHrs*SI00_fig print "%-12s\t%10s\t%8s\t%10.2f" % (mnYear,vGroup[g],sumHrs,sumSi2k) del vGroup[g] When I run the script, I get this: [root@serv07 usage]# ./test.py VOs CPU-time CPU-time kSI2K-hrs (in Sec) (in Hrs) (*2.478) ================================================== Jan, 2011 211201372 58667 145376.83 Dec, 2010 5064337 1406 3484.07 Feb, 2011 17506049 4862 12048.04 Sep, 2010 210874275 58576 145151.33 As I said in the original post, I like the result to be in this order instead: Sep, 2010 210874275 58576 145151.33 Dec, 2010 5064337 1406 3484.07 Jan, 2011 211201372 58667 145376.83 Feb, 2011 17506049 4862 12048.04 The files in the source directory reads like this: [root@serv07 usage]# ls -l total 3632 -rw-r--r-- 1 root root 1144972 Feb 9 19:23 01 -rw-r--r-- 1 root root 556630 Feb 13 09:11 02 -rw-r--r-- 1 root root 443782 Feb 11 17:23 02.bak -rw-r--r-- 1 root root 1144556 Feb 14 09:30 09 -rw-r--r-- 1 root root 370822 Feb 9 19:24 12 Did I give a better picture now? Sorry for not being very clear in the first place. Cheers!! Update @Mark Ransom This is the result from Mark's suggestion: [root@serv07 usage]# ./test.py VOs CPU-time CPU-time kSI2K-hrs (in Sec) (in Hrs) (*2.478) ========================================================== Dec, 2010 5064337 1406 3484.07 Sep, 2010 210874275 58576 145151.33 Feb, 2011 17506049 4862 12048.04 Jan, 2011 211201372 58667 145376.83 As I said before, I'm looking for the result to b printed in this order: Sep, 2010 - Dec, 2010 - Jan, 2011 - Feb, 2011 Cheers!!

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  • Pointer arithmetic.

    - by Knowing me knowing you
    Having code: int** a = new int*[2]; a[0] = new int(1); a[1] = new int(2); cout << "a[0] " << a[0] << '\n'; cout << "a[1] " << a[1] << '\n'; cout << "a[2] " << a[2] << '\n'; cout << "a[0] + 1 " << a[0] + 1 << '\n';//WHY THIS ISN'T == a[1] ? cout << "*(a + 1): " << *(a + 1) << '\n'; //WHY THIS IS == a[1] ? cout << "a[0] - a[1] " << static_cast<int>(a[0] - a[1])<< '\n';//WHY THIS IS == 16 not 4? cout << sizeof(int**); Questions are included right next to relevant lines in code.

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  • Keeping sync in multiplayer RTS game that uses floating point arithmetic

    - by Calmarius
    I'm writing a 2D space RTS game in C#. Single player works. Now I want to add some multiplayer functionality. I googled for it and it seems there is only one way to have thousands of units continuously moving without a powerful net connection: send only the commands through the network while running the same simulation at every player. And now there is a problem the entire engine uses doubles everywhere. And floating point calculations are depends heavily on compiler optimalizations and cpu architecture so it is very hard to keep things syncronized. And it is not grid based at all, and have a simple phisics engine to move the space-ships (space ships have impulse and angular-momentum...). So recoding the entire stuff to use fixed point would be quite cumbersome (but probably the only solution). So I have 2 options so far: Say bye to the current code and restart from scratch using integers Make the game LAN only where there is enough bandwidth to have 8 players with thousands of units and sending the positions and orientation etc in (almost) every frame... So I looking for better opinions, (or even tips on migrating the code to fixed-point without messing everything up...)

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  • mouse pointer moving on its own

    - by PA
    After two months of working correctly, I am experiencing an strange and very annoying problem. My mouse pointer is moving on its own. If I move the mouse to the left, as soon as I stop the movement, the pointer runs again to the far right. This makes the mouse totally unusable. The mouse device is an optical USB mouse. It is not a problem with the mouse itself. I have tried with another mouse, same problem. (both mice are OK, I have tried both mice on my laptop, both worked perfectly) Have tried different surfaces, too. Same problem. System is Windows XP Pro SP3. Computer is a desktop PC two months old. I suspected it could be a problem with the mouse driver. But both mice are from different brand, so I suppose they use different drivers. What else can I try? any suggestion?

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  • Working with a list, performing arithmetic logic in Python

    - by haea ohoh
    Suppose I have made a large list of numbers, and I want to make another one which I will add, pairwise, with the first list. Here's the first list, A: [109, 77, 57, 34, 94, 68, 96, 72, 39, 67, 49, 71, 121, 89, 61, 84, 45, 40, 104, 68, 54, 60, 68, 62, 91, 45, 41, 118, 44, 35, 53, 86, 41, 63, 111, 112, 54, 34, 52, 72, 111, 113, 47, 91, 107, 114, 105, 91, 57, 86, 32, 109, 84, 85, 114, 48, 105, 109, 68, 57, 78, 111, 64, 55, 97, 85, 40, 100, 74, 34, 94, 78, 57, 77, 94, 46, 95, 60, 42, 44, 68, 89, 113, 66, 112, 60, 40, 110, 89, 105, 113, 90, 73, 44, 39, 55, 108, 110, 64, 108] And here's B: [35, 106, 55, 61, 81, 109, 82, 85, 71, 55, 59, 38, 112, 92, 59, 37, 46, 55, 89, 63, 73, 119, 70, 76, 100, 49, 117, 77, 37, 62, 65, 115, 93, 34, 107, 102, 91, 58, 82, 119, 75, 117, 34, 112, 121, 58, 79, 69, 68, 72, 110, 43, 111, 51, 102, 39, 52, 62, 75, 118, 62, 46, 74, 77, 82, 81, 36, 87, 80, 56, 47, 41, 92, 102, 101, 66, 109, 108, 97, 49, 72, 74, 93, 114, 55, 116, 66, 93, 56, 56, 93, 99, 96, 115, 93, 111, 57, 105, 35, 99] How might I generate the arithmatic addition logic, processing each pairwise value one by one (A[0] and B[0], through A[99], B[99]) and producing the list C (A[0] + B[0] through A[99]+ B[99])?

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  • Unexpected variable update when using bash's $(( )) operator for arithmetic

    - by philo
    I'm trying to trim a few lines from a file. I know exactly how many lines to remove (say, 2 from the top), but not how many total lines are in the file. So I tried this straightforward solution: $ wc -l $FILENAME 119559 my_filename.txt $ LINES=$(wc -l $FILENAME | awk '{print $1}') $ tail -n $(($LINES - 2)) $FILENAME > $OUTPUT_FILE The output is fine, but what happened to LINES?? $ wc -l $OUTPUT_FILE 119557 my_output_file.txt $ echo $LINES 107 Hoping someone can help me understand what's going on.

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  • C++ template nontype parameter arithmetic

    - by aaa
    hello I am trying to specialize template the following way: 132 template<size_t _1,size_t _2> 131 struct integral_index_ {}; ... 141 template<size_t _1> 142 struct integral_index_<_1, _1 + 1> { ... 148 }; however I get compiler message error the template argument list of the partial specialization includes a non -type argument whose type depends on a template parameter. what do my doing wrong? thanks

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  • Arithmetic Operations in Arrays with PHP

    - by Ajith
    I have two arrays $data1 = array() $data1 = array( '10','22','30') and also another array carries $data2 = array() $data2 = array( '2','11','3'); I need to divide these two arrays(ie,$data1/$data2) and store value to $data3[]. I need to get it as follows $data3[] = array('5','2','10') If someone knows of an easy way to do this would be of great help. Thanks

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  • The unary increment operator in pointer arithmetic

    - by RhymesWithDuck
    Hello, this is my first post. I have this function for reversing a string in C that I found. void reverse(char* c) { if (*c != 0) { reverse(c + 1); } printf("%c",*c); } It works fine but if I replace: reverse(c + 1); with: reverse(++c); the first character of the original string is truncated. My question is why would are the statements not equivalent in this instance? Thanks

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  • Freeing memory with Pointer Arithmetic

    - by Breedly
    C++ newb here. I'm trying to write my own implementation of an array using only pointers, and I've hit a wall I don't know how to get over. My constructor throws this error array.cpp:40:35: error: invalid conversion from ‘int*’ to ‘int’ [-fpermissive] When my array initializes I want it to free up all the spaces in the array for ints. Array::Array(int theSize){ size = theSize; int *arrayPointer = new int; int index = 0; while(theSize > index){ *(arrayPointer + index) = new int; //This is the trouble line. ++index; } } What am I doing wrong stackoverflow?

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  • Why Garbage Collection if smart pointers are there

    - by Gulshan
    This days, so many languages are garbage collected. Even it is available for C++ by third parties. But, C++ has RAII and smart pointers. So, what's the point of using garbage collection? Is it doing something extra? And in other languages like C#, if all the references are treated as smart pointers(keeping RAII aside), by specification and by implementation, will there be still any need of garbage collectors? If no, then why this is not so?

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  • Implementing a list with unique_ptr<>? [migrated]

    - by Alexander Duchene
    As I understand it, a unique_ptr signifies exclusive ownership. A singly linked list seems to fit this, with each node owning the next, like (pseduocode alert) class node{ public: unique_ptr<node> next; int value; }; but I don't understand how to perform operations like traversing the list, where I'm used to doing here=here->next; How do you implement data structures using unique_ptr's? Are they the right tool for the job?

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  • Fixed mouse pointer with jQuery draggable

    - by MikeWyatt
    I'm building a little game in HTML5. The canvas element is a viewport into the game world. The user can move the viewport's position in the world by clicking and dragging with the mouse on a small icon. The problem is that the scrolling stops when the mouse pointer hits the edge of the screen. In all likelihood, that will limit scrolling in one of the directions severely, since the icon will be in one of the corners of the page. The only technical solution I can think of would be to somehow fix the mouse pointer's position on the icon and detect the relative movement each frame. Basically I would just reset the pointer position back to the center of the icon after each drag event. Unfortunately, I'm fairly positive that this is not possible. Playing with the user's pointer is a big no-no from a usability and security standpoint. So, is there any other way to do what I want? I'm primarily looking for technical ideas here, but suggestions for a more appropriate interface would also be welcome.

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