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  • Referencing not-yet-defined variables - Java

    - by user2537337
    Because I'm tired of solving math problems, I decided to try something more engaging with my very rusty (and even without the rust, very basic) Java skills. I landed on a super-simple people simulator, and thus far have been having a grand time working through the various steps of getting it to function. Currently, it generates an array of people-class objects and runs a for loop to cycle through a set of actions that alter the relationships between them, which I have stored in a 2d integer array. When it ends, I go look at how much they all hate each other. Fun stuff. Trouble has arisen, however, because I would like the program to clearly print what action is happening when it happens. I thought the best way to do this would be to add a string, description, to my "action" class (which stores variables for the actor, reactor, and the amount the relationship changes). This works to a degree, in that I can print a generic message ("A fight has occurred!") with no problem. However, ideally I would like it to be a little more specific ("Person A has thrown a rock at Person B's head!"). This latter goal is proving more difficult: attempting to construct an action with a description string that references actor and reactor gets me a big old error, "Cannot reference field before it is defined." Which makes perfect sense. I believe I'm not quite in programmer mode, because the only other way I can think to do this is an unwieldy switch statement that negates the need for each action to have its own nicely-packaged description. And there must be a neater way. I am not looking for examples of code, only a push in the direction of the right concept to handle this.

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  • how to append a string to next line in perl

    - by tprayush
    hi all , i have a requirement like this.. this just a sample script... $ cat test.sh #!/bin/bash perl -e ' open(IN,"addrss"); open(out,">>addrss"); @newval; while (<IN>) { @col_val=split(/:/); if ($.==1) { for($i=0;$i<=$#col_val;$i++) { print("Enter value for $col_val[$i] : "); chop($newval[$i]=<STDIN>); } $str=join(":"); $_="$str" print OUT; } else { exit 0; } } close(IN); close(OUT); ' when i run this scipt... $ ./test.sh Enter value for NAME : abc Enter value for ADDRESS : asff35 Enter value for STATE : XYZ Enter value for CITY : EIDHFF Enter value for CONTACT : 234656758 $ cat addrss NAME:ADDRESS:STATE:CITY:CONTACT abc:asff35:XYZ:EIDHFF:234656758 when ran it second time $ cat addrss NAME:ADDRESS:STATE:CITY:CONTACT abc:asff35:XYZ:EIDHFF:234656758ioret:56fgdh:ghdgh:afdfg:987643221 ## it is appended in the same line... i want it to be added to the next line..... NOTE: i want to do this by explitly using the filehandles in perl....and not with redirection operators in shell. please help me!!!

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  • How to create and display a list in Java?

    - by lox
    i have to create a list of ,let's say 50 people, (in Java) and display the list, and i don't really know how to do that. so this is what i have tried to do so far . please correct and complete some of my code . public class Person { String name; String stuff; } public class CreatePerson { public static void ang() { ArrayList<Person> thing=new ArrayList<Person>(); Scanner diskScanner = new Scanner(in); for(int i=0; i<50; i++){ Person pers = new Person(); out.print("name: "); pers.name=diskScanner.nextLine(); out.print("stuff: "); pers.stuff=diskScanner.nextLine(); thing.add(pers); break; } // Display people for (int i=0; i<50; i++) { out.println(??);{ } } }}

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  • What is the Pythonic way to implement a simple FSM?

    - by Vicky
    Yesterday I had to parse a very simple binary data file - the rule is, look for two bytes in a row that are both 0xAA, then the next byte will be a length byte, then skip 9 bytes and output the given amount of data from there. Repeat to the end of the file. My solution did work, and was very quick to put together (even though I am a C programmer at heart, I still think it was quicker for me to write this in Python than it would have been in C) - BUT, it is clearly not at all Pythonic and it reads like a C program (and not a very good one at that!) What would be a better / more Pythonic approach to this? Is a simple FSM like this even still the right choice in Python? My solution: #! /usr/bin/python import sys f = open(sys.argv[1], "rb") state = 0 if f: for byte in f.read(): a = ord(byte) if state == 0: if a == 0xAA: state = 1 elif state == 1: if a == 0xAA: state = 2 else: state = 0 elif state == 2: count = a; skip = 9 state = 3 elif state == 3: skip = skip -1 if skip == 0: state = 4 elif state == 4: print "%02x" %a count = count -1 if count == 0: state = 0 print "\r\n"

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  • Help thinking "Pythony"

    - by Josh
    I'm brand new to Python and trying to learn it by replicating the following C++ function into python // determines which words in a vector consist of the same letters // outputs the words with the same letters on the same line void equivalentWords(vector <string> words, ofstream & outFile) { outFile << "Equivalent words\n"; // checkedWord is parallel to the words vector. It is // used to make sure each word is only displayed once. vector <bool> checkedWord (words.size(), false); for(int i = 0; i < words.size(); i++) { if (!checkedWord[i]){ outFile << " "; for(int j = i; j < words.size(); j++){ if(equivalentWords(words[i], words[j], outFile)) { outFile << words[j] << " "; checkedWord[j] = true; } } outFile << "\n"; } } } In my python code (below), rather than having a second vector, I have a list ("words") of lists of a string, a sorted list of the chars in the former string (because strings are immutable), and a bool (that tells if the word has been checked yet). However, I can't figure out how to change a value as you iterate through a list. for word, s_word, checked in words: if not checked: for word1, s_word1, checked1 in words: if s_word1 == s_word: checked1 = True # this doesn't work print word1, print "" Any help on doing this or thinking more "Pythony" is appreciated.

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  • execute a string of PHP code on the command line

    - by Matthew J Morrison
    I'd like to be able to run a line of PHP code on the command line similar to how the following options work: :~> perl -e "print 'hi';" :~> python -c "print 'hi'" :~> ruby -e "puts 'hi'" I'd like to be able to do: :~> php "echo 'hi';" I've read that there is a -r option that can do what I need for php, however it doesn't appear to be available when I try to use it. I've tried using PHP 5.2.13 and PHP 4.4.9 and neither have an -r option available. I wrote this script (that I called run_php.php) - which works, but I'm not a huge fan of it just because I feel like there should be a more "correct" way to do it. #!/usr/bin/php5 -q <?php echo eval($argv[1]); ?> My question is: is there a -r option? If so, why is it not available when I run --help? If there is no -r option, what is the best way to do this (without writing an intermediary script if possible)? Thanks!

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  • Reverse reading WORD from a binary file?

    - by Angel
    Hi, I have a structure: struct JFIF_HEADER { WORD marker[2]; // = 0xFFD8FFE0 WORD length; // = 0x0010 BYTE signature[5]; // = "JFIF\0" BYTE versionhi; // = 1 BYTE versionlo; // = 1 BYTE xyunits; // = 0 WORD xdensity; // = 1 WORD ydensity; // = 1 BYTE thumbnwidth; // = 0 BYTE thumbnheight; // = 0 }; This is how I read it from the file: HANDLE file = CreateFile(filename, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0); DWORD tmp = 0; DWORD size = GetFileSize(file, &tmp); BYTE *DATA = new BYTE[size]; ReadFile(file, DATA, size, &tmp, 0); JFIF_HEADER header; memcpy(&header, DATA, sizeof(JFIF_HEADER)); This is how the beginning of my file looks in hex editor: 0xFF 0xD8 0xFF 0xE0 0x00 0x10 0x4A 0x46 0x49 0x46 0x00 0x01 0x01 0x00 0x00 0x01 When I print header.marker, it shows exactly what it should (0xFFD8FFE0). But when I print header.length, it shows 0x1000 instead of 0x0010. The same thing is with xdensity and ydensity. Why do I get wrong data when reading a WORD? Thank you.

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  • How to make categories and current page highlighting in PHP?

    - by Markus Ossi
    I am trying to find some example code or best practices about making CMS-type categories with PHP. This is a problem that has for sure been solved gazillion times but for some reason I am unable to find any example code using PHP about how to implement this. As far as I can tell, there are two parts to the problem. The first one has to with the styling side of things: outputting the link in the navigation so that the current page has a special style (class="active") and to not print out the link for the current page. The second part is handling categories, subcategories and the dynamic pages under the categories. The second part seems pretty straightforward. I am thinking of making it so that the name of the category in the navigation is a link to categories.php?id=x and on this page I just print out the pages with that category id. Then, if the user klicks on a page he will be taken to pages.php?id=y. However, I am not quite sure on how to make a navigation to check if we are now on the current page. Should I just use some case switch or what? Any ideas or links to some good example code are much appreciated.

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  • Where can we use "This" in Recursion methode...

    - by T_Geek
    Hi . I have a methode in a static class which try to convert bi*nar*y tre to list I'd like to make a recusion but I couldn't I've implemented some opertation in my class like add,delet,find.it's too easy to implement its . Here is the code class ARB { private: struct BT { int data; BT *l; BT *r; }; struct BT *p; public ARB(); ~ARB(); void del(int n); void add(int n); }; void ARB::del(int num) { //The code ,don't care about it }; main() { // BTR T; T.add(3); T.add(5); }; Here is what should we do to transfert the code from Benary tree tolist LLC ARB::changeit() { LLC x; while(this!=NULL) { x.add(this->data); // if(this.l==NULL) { x.print(); //To print the elemnts of List return(x); } else { x=changeit(this.l); } if(this.r!=NULL) { x.~LLC(); x=changeit(this.r); return(x); } } }

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  • java programming

    - by Baiba
    ok i have version of t code, please tell me what i need to do when i need to get out of program The INDEX NUMBER OF COLUMN IN WHICH ARE LEAST ZEROS? class Uzd{ public static void main(String args[]){ int mas[][]= {{3,4,7,5,0}, {4,5,3,0,1}, {8,2,4,0,3}, {7,0,2,0,1}, {0,0,1,3,0}}; int nul_mas[] = new int[5]; int nul=0; for(int j=0;j<5;j++){// nul=0; for(int i=0;i<5;i++){ if(mas[i][j]==0){ nul++; } } nul_mas[j]=nul; } for(int i=0;i<5;i++){ for(int j=0;j<5;j++){ System.out.print(mas[i][j]); } System.out.println(); } System.out.println();// atstarpe System.out.println("///zeros in each column///"); for(int i=0;i<5;i++){System.out.print(nul_mas[i]);} System.out.println(); }} and after running it shows: 34750 45301 82403 70201 00130 ///zeros in each column/// But i need not in each column but i need to get out index of column in which zeros are least! in this situation it is column nubmer 2!! 12032

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  • Managing libraries and imports in a programming language

    - by sub
    I've created an interpreter for a stupid programming language in C++ and the whole core structure is finished (Tokenizer, Parser, Interpreter including Symbol tables, core functions, etc.). Now I have a problem with creating and managing the function libraries for this interpreter (I'll explain what I mean with that later) So currently my core function handler is horrible: // Simplified version myLangResult SystemFunction( name, argc, argv ) { if ( name == "print" ) { if( argc < 1 ) { Error('blah'); } cout << argv[ 0 ]; } else if ( name == "input" ) { if( argc < 1 ) { Error('blah'); } string res; getline( cin, res ); SetVariable( argv[ 0 ], res ); } else if ( name == "exit ) { exit( 0 ); } And now think of each else if being 10 times more complicated and there being 25 more system functions. Unmaintainable, feels horrible, is horrible. So I thought: How to create some sort of libraries that contain all the functions and if they are imported initialize themselves and add their functions to the symbol table of the running interpreter. However this is the point where I don't really know how to go on. What I wanted to achieve is that there is e.g.: an (extern?) string library for my language, e.g.: string, and it is imported from within a program in that language, example: import string myString = "abcde" print string.at( myString, 2 ) # output: c My problems: How to separate the function libs from the core interpreter and load them? How to get all their functions into a list and add it to the symbol table when needed? What I was thinking to do: At the start of the interpreter, as all libraries are compiled with it, every single function calls something like RegisterFunction( string namespace, myLangResult (*functionPtr) ); which adds itself to a list. When import X is then called from within the language, the list built with RegisterFunction is then added to the symbol table. Disadvantages that spring to mind: All libraries are directly in the interpreter core, size grows and it will definitely slow it down.

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  • This code is not submitting to a form? Why

    - by Ankur
    Since I am using get I expect to see the submitted values appended to the queryString but instead all I see is the URL of the servlet being called with nothing added at the end. <form id="editClassList" name="editClassList" method="get" action="EditClassList"> <% HashMap<Integer,String> classes = new HashMap<Integer,String>(); classes = (HashMap<Integer,String>) request.getAttribute("classes"); %> <% if(classes.size()==0){ %> <label><input class="small-link" type="text" id="add-this-class" size="42" value="" /></label> <% } %> <% Set<Integer> classIds = new HashSet<Integer>(); classIds = classes.keySet(); Iterator<Integer> itr = classIds.iterator(); while(itr.hasNext()){ int nextId = (Integer)itr.next(); %> <label><input class="small-link" type="text" id="<% out.print(nextId); %>" size="42" value="<% out.print(classes.get(nextId)); %>" /> </label> <img id="add-class" src="images/add.png" width="16" height="16" /><br /> <label><input class="small-link" type="text" id="class-to-add" size="42" value="" /></label> <% } %> <label><input type="submit" id="save-class-btn" value="Save Class(es)" /></label> </form>

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  • Java import statement

    - by nattyP
    I am using java on debian 5 java version "1.6.0_20" Java(TM) SE Runtime Environment (build 1.6.0_20-b02) Java HotSpot(TM) Client VM (build 16.3-b01, mixed mode, sharing) Why is there a difference between the following Case 1: import java.util.*; Case 2: import java.util.*; import java.util.Arrays; import java.util.List; Why doesnt the first case cover the second case? The code only compiles when I import Arrays and List explicitly. Code: import java.util.*; import java.util.Arrays; import java.util.List; public class Test { public static void main (String[] args) { List<Integer> i = new ArrayList(Arrays.asList(1,2,3,4,5,6,7,8,9,10)); List<Integer> j = new ArrayList(); ListIterator<Integer> n = i.listIterator(i.size()); while(n.hasPrevious()) { j.add(n.previous()); } println(j); } static void println(Object o) { System.out.println(o); } static void print(Object o) { System.out.print(o); } }

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  • Ruby: counters, counting and incrementing

    - by Shyam
    Hi, If you have seen my previous questions, you'd already know I am a big nuby when it comes to Ruby. So, I discovered this website which is intended for C programming, but I thought whatever one can do in C, must be possible in Ruby (and more readable too). The challenge is to print out a bunch of numbers. I discovered this nifty method .upto() and I used a block (and actually understanding its purpose). However, in IRb, I got some unexpected behavior. class MyCounter def run 1.upto(10) { |x| print x.to_s + " " } end end irb(main):033:0> q = MyCounter.new => #<MyCounter:0x5dca0> irb(main):034:0> q.run 1 2 3 4 5 6 7 8 9 10 => 1 I have no idea where the = 1 comes from :S Should I do this otherwise? I am expecting to have this result: 1 2 3 4 5 6 7 8 9 10 Thank you for your answers, comments and feedback!

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  • How Optimize sql query make it faster

    - by user502083
    Hello every one : I have a very simple small database, 2 of tables are: Node (Node_ID, Node_name, Node_Date) : Node_ID is primary key Citation (Origin_Id, Target_Id) : PRIMARY KEY (Origin_Id, Target_Id) each is FK in Node Now I write a query that first find all citations that their Origin_Id has a specific date and then I want to know what are the target dates of these records. I'm using sqlite in python the Node table has 3000 record and Citation has 9000 records, and my query is like this in a function: def cited_years_list(self, date): c=self.cur try: c.execute("""select n.Node_Date,count(*) from Node n INNER JOIN (select c.Origin_Id AS Origin_Id, c.Target_Id AS Target_Id, n.Node_Date AS Date from CITATION c INNER JOIN NODE n ON c.Origin_Id=n.Node_Id where CAST(n.Node_Date as INT)={0}) VW ON VW.Target_Id=n.Node_Id GROUP BY n.Node_Date;""".format(date)) cited_years=c.fetchall() self.conn.commit() print('Cited Years are : \n ',str(cited_years)) except Exception as e: print('Cited Years retrival failed ',e) return cited_years Then I call this function for some specific years, But it's crazy slowwwwwwwww :( (around 1 min for a specific year) Although my query works fine, it is slow. would you please give me a suggestion to make it faster? I'd appreciate any idea about optimizing this query :) I also should mention that I have indices on Origin_Id and Target_Id, so the inner join should be pretty fast, but it's not!!!

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  • Passing a Batch File an Argument Containing a Quote Containing a Space

    - by Synetech inc.
    Hi, On many occasions I have dealt with passing batch files arguments with spaces, quotes, percents, and slashes and all sorts of combinations of them. Usually I managed to figure out how to accomplish what I want, but this time I am stuck. I have tried a couple of hundred combinations now and my head is starting to hurt. I’ve reduced the problem quite nicely. It’s a simple requirement: pass a double-quoted space from one batch file to another. That is, one batch file should pass some string X to another so that the the second one echos " ". I just can’t figure out what X should be. Here is a minimal batch file that demonstrates and attempt that does not work. (This BAT file takes the place of both by calling itself.) ::Goal is to print: ::" " ::That is, to pass a quoted space from a BAT file to a BAT file if not (%1)==() goto recurse %0 "" "" :recurse echo %1 pause It does not work. I’ve tried using "\" \"", """ """, """" """", "\"" "\"", ""\" \""", "^" ^"", ^"" "^", and so on. Either they print double double-quotes, lose everything after the space, or something else (that is wrong). Any ideas? Thanks.

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  • In Perl, how can I wait for threads to end in parallel?

    - by Pmarcoen
    I have a Perl script that launches 2 threads,one for each processor. I need it to wait for a thread to end, if one thread ends a new one is spawned. It seems that the join method blocks the rest of the program, therefore the second thread can't end until everything the first thread does is done which sort of defeats its purpose. I tried the is_joinable method but that doesn't seem to do it either. Here is some of my code : use threads; use threads::shared; @file_list = @ARGV; #Our file list $nofiles = $#file_list + 1; #Real number of files $currfile = 1; #Current number of file to process my %MSG : shared; #shared hash $thr0 = threads->new(\&process, shift(@file_list)); $currfile++; $thr1 = threads->new(\&process, shift(@file_list)); $currfile++; while(1){ if ($thr0->is_joinable()) { $thr0->join; #check if there are files left to process if($currfile <= $nofiles){ $thr0 = threads->new(\&process, shift(@file_list)); $currfile++; } } if ($thr1->is_joinable()) { $thr1->join; #check if there are files left to process if($currfile <= $nofiles){ $thr1 = threads->new(\&process, shift(@file_list)); $currfile++; } } } sub process{ print "Opening $currfile of $nofiles\n"; #do some stuff if(some condition){ lock(%MSG); #write stuff to hash } print "Closing $currfile of $nofiles\n"; } The output of this is : Opening 1 of 4 Opening 2 of 4 Closing 1 of 4 Opening 3 of 4 Closing 3 of 4 Opening 4 of 4 Closing 2 of 4 Closing 4 of 4

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  • Invoking a method overloaded where all arguments implement the same interface

    - by double07
    Hello, My starting point is the following: - I have a method, transform, which I overloaded to behave differently depending on the type of arguments that are passed in (see transform(A a1, A a2) and transform(A a1, B b) in my example below) - All these arguments implement the same interface, X I would like to apply that transform method on various objects all implementing the X interface. What I came up with was to implement transform(X x1, X x2), which checks for the instance of each object before applying the relevant variant of my transform. Though it works, the code seems ugly and I am also concerned of the performance overhead for evaluating these various instanceof and casting. Is that transform the best I can do in Java or is there a more elegant and/or efficient way of achieving the same behavior? Below is a trivial, working example printing out BA. I am looking for examples on how to improve that code. In my real code, I have naturally more implementations of 'transform' and none are trivial like below. public class A implements X { } public class B implements X { } interface X { } public A transform(A a1, A a2) { System.out.print("A"); return a2; } public A transform(A a1, B b) { System.out.print("B"); return a1; } // Isn't there something better than the code below??? public X transform(X x1, X x2) { if ((x1 instanceof A) && (x2 instanceof A)) { return transform((A) x1, (A) x2); } else if ((x1 instanceof A) && (x2 instanceof B)) { return transform((A) x1, (B) x2); } else { throw new RuntimeException("Transform not implemented for " + x1.getClass() + "," + x2.getClass()); } } @Test public void trivial() { X x1 = new A(); X x2 = new B(); X result = transform(x1, x2); transform(x1, result); }

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  • Why does my Perl CGI program fail with "Software error: ..."?

    - by kiran
    When I try to run my Perl CGI program, the returned web page tells me: Software error: For help, please send mail to the webmaster (root@localhost), giving this error message and the time and date of the error. Here is my code in one of the file: #!/usr/bin/perl use lib "/home/ecoopr/ecoopr.com/CPAN"; use CGI; use CGI::FormBuilder; use CGI::Session; use CGI::Carp (fatalsToBrowser); use CGI::Session; use HTML::Template; use MIME::Base64 (); use strict; require "./db_lib.pl"; require "./config.pl"; my $query = CGI-new; my $url = $query-url(); my $hostname = $query-url(-base = 1); my $login_url = $hostname . '/login.pl'; my $redir_url = $login_url . '?d=' . $url; my $domain_name = get_domain_name(); my $helpful_msg = $query-param('m'); my $new_trusted_user_fname = $query-param('u'); my $action = $query-param('a'); $new_trusted_user_fname = MIME::Base64::decode($new_trusted_user_fname); ####### Colin: Added July 12, 2009 ####### my $view = $query-param('view'); my $offset = $query-param('offset'); ####### Colin: Added July , 2009 ####### #print $session-header; #print $new_trusted_user; my $helpful_msg_txt = qq[]; my $helpful_msg_div = qq[]; if ($helpful_msg)

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  • WN server filter won't work

    - by Mike Fink
    WN servers have an alternative to cgi programs called filters. I have been trying to get one to work, but I have had no luck. I am writing in python. It looks like the server is not receiving any output from the program but is parsing nothing and wrapping this nothing in my standard header and footer. I have chmod 755 the program and my index.wn file reads: Default-Attributes=parse Default-Wrappers=templates/template1.inc File=includeTests.html File=index.html File=archives.html File=contact.html File=style.css File=testProgram.py #here is the stuff about the filter File=testFilter.html Content-type=text/html Filter=testProgram.py Attributes=parse, cgi here is what is in the filter called testProgram.py: #!/usr/bin/python print "Content-Type: text/html\n\n" print "hi" testProgram.py works perfectly if it is shoved into a cgi-bin folder and chmoded. I suppose my problem may lay with the fact that I have never ever seen a filter program in python. I'm not sure I have even seen a filter program at all. Does anyone out there have any experience with wn servers and filters? Any ideas?

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  • Perl regex which grabs ALL double letter occurances in a line

    - by phileas fogg
    Hi all, still plugging away at teaching myself Perl. I'm trying to write some code that will count the lines of a file that contain double letters and then place parentheses around those double letters. Now what I've come up with will find the first ocurrance of double letters, but not any other ones. For instance, if the line is: Amp, James Watt, Bob Transformer, etc. These pioneers conducted many My code will render this: 19 Amp, James Wa(tt), Bob Transformer, etc. These pioneers conducted many The "19" is the count (of lines containing double letters) and it gets the "tt" of "Watt" but misses the "ee" in "pioneers". Below is my code: $file = '/path/to/file/electricity.txt'; open(FH, $file) || die "Cannot open the file\n"; my $counter=0; while (<FH>) { chomp(); if (/(\w)\1/) { $counter += 1; s/$&/\($&\)/g; print "\n\n$counter $_\n\n"; } else { print "$_\n"; } } close(FH); What am I overlooking? TIA!

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  • Terminal-based snake game: input thread manipulates output

    - by enlightened
    I'm writing a snake game for the terminal, i.e. output via print. The following works just fine: while status[snake_monad] do print to_string draw canvas, compose_all([ frame, specs, snake_to_hash(snake[snake_monad]) ]) turn! snake_monad, get_dir move! snake_monad, specs sleep 0.25 end But I don't want the turn!ing to block, of course. So I put it into a new Thread and let it loop: Thread.new do loop do turn! snake_monad, get_dir end end while status[snake_monad] do ... # no turn! here ... end Which also works logically (the snake is turning), but the output is somehow interspersed with newlines. As soon as I kill the input thread (^C) it looks normal again. So why and how does the thread have any effect on my output? And how do I work around this issue? (I don't know much about threads, even less about them in ruby. Input and output concurrently on the same terminal make the matter worse, I guess...) Also (not really important): Wanting my program as pure as possible, would it be somewhat easily possible to get the input non-blockingly while passing everything around? Thank you!

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  • Accessing program information that gdb sees in C++

    - by anon
    I have a program written in C++, on Linux, compiled with -g. When I run it under gdb, I can 1) set breakpoints 2) at those breakpoints, print out variables 3) see the stackframe 4) given a variable that's a structure, print out parts of the structure (i.e. how ddd displays information). Now, given that my program is compiled with "-g" -- is there anyway that I can access this power within my program itself? I.e. given that my program is compiled with "-g", is there some std::vector<string> getStackFrame(); function I can call to get the current stackframe at the current point of execution? Given a pointer to an object and it's type ... can I do std::vector getClassMember(class_name); ? I realize the default answer is "no, C++ doesn't support that level of introspection" -- however, recall I'm on linux, my program is compiled with "-g", and gdb can do it, so clearly the inforamtion is there. Question is: is there some API for accessing it? EDIT: PS Naysers, I'd love to see a reason for closing this question.

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  • Deleting elements from stl set while iterating through it does not invalidate the iterators.

    - by pedromanoel
    I need to go through a set and remove elements that meet a predefined criteria. This is the test code I wrote: #include <set> #include <algorithm> void printElement(int value) { std::cout << value << " "; } int main() { int initNum[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; std::set<int> numbers(initNum, initNum + 10); // print '0 1 2 3 4 5 6 7 8 9' std::for_each(numbers.begin(), numbers.end(), printElement); std::set<int>::iterator it = numbers.begin(); // iterate through the set and erase all even numbers for (; it != numbers.end(); ++it) { int n = *it; if (n % 2 == 0) { // wouldn't invalidate the iterator? numbers.erase(it); } } // print '1 3 5 7 9' std::for_each(numbers.begin(), numbers.end(), printElement); return 0; } At first, I thought that erasing an element from the set while iterating through it would invalidate the iterator, and the increment at the for loop would have undefined behavior. Even though, I executed this test code and all went well, and I can't explain why. My question: Is this the defined behavior for std sets or is this implementation specific? I am using gcc 4.3.3 on ubuntu 10.04 (32-bit version), by the way. Thanks!

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  • python list/dict property best practice

    - by jterrace
    I have a class object that stores some properties that are lists of other objects. Each of the items in the list has an identifier that can be accessed with the id property. I'd like to be able to read and write from these lists but also be able to access a dictionary keyed by their identifier. Let me illustrate with an example: class Child(object): def __init__(self, id, name): self.id = id self.name = name class Teacher(object): def __init__(self, id, name): self.id = id self.name = name class Classroom(object): def __init__(self, children, teachers): self.children = children self.teachers = teachers classroom = Classroom([Child('389','pete')], [Teacher('829','bob')]) This is a silly example, but it illustrates what I'm trying to do. I'd like to be able to interact with the classroom object like this: #access like a list print classroom.children[0] #append like it's a list classroom.children.append(Child('2344','joe')) #delete from like it's a list classroom.children.pop(0) But I'd also like to be able to access it like it's a dictionary, and the dictionary should be automatically updated when I modify the list: #access like a dict print classroom.childrenById['389'] I realize I could just make it a dict, but I want to avoid code like this: classroom.childrendict[child.id] = child I also might have several of these properties, so I don't want to add functions like addChild, which feels very un-pythonic anyway. Is there a way to somehow subclass dict and/or list and provide all of these functions easily with my class's properties? I'd also like to avoid as much code as possible.

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