Control Structures: Difference between revisions
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==[[Javascript]]== |
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[[Category:Javascript]] |
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===foreach=== |
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//iterate through properties of an object as if through a collection |
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var obj = {prop1:"a",prop2:"b",prop3:"c"}; |
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for (var key in obj) |
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alert(obj[key]); |
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Revision as of 16:57, 25 January 2007
Control Structures
You are encouraged to solve this task according to the task description, using any language you may know.
You are encouraged to solve this task according to the task description, using any language you may know.
Control structures are features of programming languages that influence the code flow. Two common examples are loops and conditions. The task here is to demonstrate control structures supported by different programming languages.
This page is being split into multiple articles. Please help move code into these articles, instead:
Iterative
These control structure operate on datasets.
C++
for_each
Compiler: GCC 4.1.1
#include <iostream> // std::cout, std::endl #include <vector> // std::vector #include <algorithm> // std::for_each struct sum { int _sum; sum() : _sum(0) {}; // Initialize sum with 0; void operator() (int a) { _sum += a; } // this function will be called for every element }; int main() { std::vector<int> v; v.push_back(10); v.push_back(23); v.push_back(34); /* Note that for_each gets a fresh instance of sum passed, * applies every element beginning with *v.begin() up to, * but not including v.end() to the function object * and returns a copy of it. */ sum the_sum = std::for_each(v.begin(), v.end(), sum()); std::cout << "The sum is " << the_sum._sum << std::endl; return 0; }
Perl
for
Interpreter: Perl 5.8.8
#!/usr/bin/perl -w use strict; my $limit = 5; for ( my $iterator = 0; $iterator < $limit; $iterator++ ) { # Do something } # for-variant, implicit iteration for (0..$limit) { # Do something } do_something() for 0..$limit;
foreach
Interpreter: Perl 5.8.8
#!/usr/bin/perl -w use strict; my @numbers = (1, 2, 3); my %names = (first => "George", last => "Jetson"); foreach my $number (@numbers) { # Do something with $number } foreach my $key (keys %names) { # Do something with $key (values are accessible as %names{$key} ) }
map
Interpreter: Perl 5.8.8
#!/usr/bin/perl -w use strict; my @numbers = (1, 2, 3); my @target; @target = map { # Do something with $_ } @numbers; @target = map($_ + 1, @numbers); sub a_sub { # Do something with $_ } @target = map a_sub @numbers;
grep
Interpreter: Perl 5.8.8
#!/usr/bin/perl -w use strict; my @people = qw/Bobbie Charlie Susan/; my @target; @target = grep { # Discriminate based on $_ } @people; # Feed grep into map, this picks out elements 1, 3, 5, etc. @target = map($people[$_], grep($_ & 1, 0..$#people)); # Pick out the diminutive names @target = grep(/ie$/, @people); sub a_sub { # Do something with $_, and return a true or false value } @target = grep a_sub @people;
Python
for
for x in ["foo", "bar", "baz"]: print x
Ruby
each
['foo', 'bar', 'baz'].each do |x| puts x end
collect
array = ['foo', 'bar', 'baz'].collect do |x| foo x end
map
array = ['foo', 'bar', 'baz'].map {|x| foo x }
inject
string = ['foo', 'bar', 'baz'].inject("") do |s,x| s << x s end
sum = ['foo', 'bar', 'baz'].inject(0) do |s,x| s + x.size s end
product = ['foo', 'bar', 'baz'].inject(1) do |p,x| p * x.size p end
hash = ['foo', 'bar', 'baz'].inject({}) do |h,x| h[x] = x.size h end
boolean = ['foo', 'bar', 'baz'].inject(true) do |b,x| b &&= x != 'bar' b end
Tcl
foreach
foreach i {foo bar baz} { puts "$i" }
UNIX Shell
for
Interpreter: Bourne Again SHell
#!/bin/bash ARRAY="VALUE1 VALUE2 VALUE3 VALUE4 VALUE5" for ELEMENT in $ARRAY do echo $ELEMENT # Print $ELEMENT done
Interpreter: Debian Almquist SHell
#!/bin/sh ARRAY="VALUE1 VALUE2 VALUE3 VALUE4 VALUE5" for ELEMENT in $ARRAY do echo $ELEMENT # Print $ELEMENT done