Loop structures: Difference between revisions
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In this task, we document loop structures offered by different languages. |
In this task, we document loop structures offered by different languages. |
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Revision as of 02:34, 1 February 2007
You are encouraged to solve this task according to the task description, using any language you may know.
In this task, we document loop structures offered by different languages.
AppleScript
repeat-until
set i to 5 repeat until i is less than 0 set i to i - 1 end repeat
repeat --endless loop end repeat
repeat-with
repeat with i from 1 to 20
--do something
end repeat
set array to {1,2,3,4,5}
repeat with i in array
display dialog i
end repeat
C
while
Compiler: GCC 4.1.2
int main (int argc, char ** argv) {
int condition = 1;
while ( condition ) {
// Do something
// Don't forget to change the value of condition.
// If it remains nonzero, we'll have an infinite loop.
}
}
do-while
int main (int argc, char ** argv) {
int condition = ...;
do {
// Do something
// The difference with the first loop is that the
// code in the loop will be executed at least once,
// even if the condition is 0 at the beginning,
// because it is only checked at the end.
// Don't forget to change the value of condition.
// If it remains nonzero, we'll have an infinite loop.
} while ( condition );
}
for
int main (int argc, char ** argv) {
int i;
for {i=0; i<10; ++i) {
// The code here will be performed 10 times.
// The first part in the for-statement (i=0) is the initialization,
// and is executed once before the loop begins.
// The second part is the end condition (i<10), which is checked
// every time the loop is started, also the first time;
// the loop ends if it is false.
// The third part (++i) is performed every time the code in the loop
// is at the end, just before the end condition is checked.
}
}
while with continue
The continue statement allows you to continue execution at the beginning of the loop, skipping the rest of the loop. In C you can only do this with the most inner loop. You can also do this with do-while and for.
int main (int argc, char ** argv) {
int condition = 1;
while ( condition ) {
// Do something
if (other condition)
continue; // Continue at the beginning of the loop
// Do something else
// This part is not executed if other condition was true
}
}
while with break
The break statement allows you to stop a loop. In C you can only break from most inner loop. You can also do this with do-while and for.
int main (int argc, char ** argv) {
int condition = 1;
while ( condition ) {
// Do something
if (other condition)
break; // Continue after the the loop
// Do something else
// This part is not executed if other condition was true
}
}
C++
Run-Time Control Structures
for
Compiler: GCC 3.3.4
#include <iostream>
int main()
{
int i = 1;
// Loops forever:
for(; i == 1;)
std::cout << "Hello, World!\n";
}
do-while
Compiler: GCC 4.1.2
int main (void) {
int condition = 1;
do {
// Do something
// Don't forget to change the value of condition.
// If it remains nonzero, we'll have an infinite loop.
} while ( condition );
}
Run-Time Control Structures
while
Compiler: GCC 4.1.2
int main (void) {
int condition = 1;
while ( condition ) {
// Do something
// Don't forget to change the value of condition.
// If it remains nonzero, we'll have an infinite loop.
}
}
do-while
Compiler: GCC 4.1.2
int main (void) {
int condition = 1;
do {
// Do something
// Don't forget to change the value of condition.
// If it remains nonzero, we'll have an infinite loop.
} while ( condition );
}
Java
while
while(true)
{
foo();
}
do-while
do
{
foo();
}
while (true)
for
for(int i = 0; i < 5; i++)
{
foo();
}
foreach
Platform: J2SE 1.5.0
Object[] objects;
// ...
for (Object current : objects[]) {
// ...
}
int[] numbers;
// ...
for (int i : numbers) {
// ...
}
JavaScript
while
while(true) {
foo();
}
do while
do {
foo();
} while(test);
for
for(var i = 0; i < 5; i++) {
foo();
}
for in
//iterate through property names of an object
var obj = {prop1:"a", prop2:"b", prop3:"c"};
for (var key in obj)
alert( key + ' is set to ' + obj[key] );
for each in
//iterate through property values of an object
var obj = {prop1:"a", prop2:"b", prop3:"c"};
for each(var element in obj)
alert( element );
Pascal
while
Compiler: Turbo Pascal 7.0
WHILE condition1 DO
BEGIN
procedure1;
procedure2;
END;
repeat-until
Compiler: Turbo Pascal 7.0
REPEAT procedure1; procedure2; UNTIL condition1;
for
Compiler: Turbo Pascal 7.0
FOR counter=1 TO 10 DO
BEGIN
procedure1;
procedure2;
END;
Perl
while
Interpreter: Perl 5.8.8
#!/usr/bin/perl -w
use strict;
my $condition1 = 0;
while ( $condition1 ) {
# Do something.
# Remember to change the value of condition1 at some point.
}
do-while
Interpreter: Perl 5.8.8
#!/usr/bin/perl -w
use strict;
my $condition1 = 0;
do {
# Do something.
# Remember to change the value of condition1 at some point.
} while ( $condition1 );
until
Interpreter: Perl 5.8.8
#!/usr/bin/perl -w
use strict;
my $condition1 = 1;
until ( $condition1 ) {
# Do something.
# Remember to change the value of condition1 at some point.
}
do-until
Interpreter: Perl 5.8.8
#!/usr/bin/perl -w
use strict;
my $condition1 = 1;
do {
# Do something.
# Remember to change the value of condition1 at some point.
} until ( $condition1 );
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 $_, and return a true or false value
}
@target = grep a_sub @people;
PHP
while
while(ok()) {
foo();
bar();
baz();
}
for
for($i = 0; $i < 10; ++$i) {
echo $i;
}
foreach
foreach(range(0, 9) as $i) {
echo $i;
}
Python
with
Interpreter: Python 2.5
foo could for example open a file or create a lock or a database transaction:
with foo() as bar: baz(bar)
while
while ok():
foo()
bar()
baz()
else:
# break was not called
quux()
for
for i in range(10):
print i
else:
# break was not called
foo()
for x in ["foo", "bar", "baz"]:
print x
Does range(10) return an array? The above two examples may be redundant.
Ruby
while
while true do foo end
for
for i in [0..4] do foo end
each
['foo', 'bar', 'baz'].each do |x| puts x end
collect
array = ['foo', 'bar', 'baz'].collect do |x| foo x end
map
array = ['foo', 'bar', 'baz'].map {|x| foo x }
inject
string = ['foo', 'bar', 'baz'].inject("") do |s,x|
s << x
end
sum = ['foo', 'bar', 'baz'].inject(0) do |s,x| s + x.size end
product = ['foo', 'bar', 'baz'].inject(1) do |p,x| p * x.size end
boolean = ['foo', 'bar', 'baz'].inject(true) do |b,x| b &&= x != 'bar' end
Smalltalk
whileTrue/whileFalse
x := 0.
[ x < 100 ]
whileTrue: [ x := x + 10.].
[ x = 0 ]
whileFalse: [ x := x - 20.].
Tcl
foreach
foreach i {foo bar baz} {
puts "$i"
}
for
for {set i 0} {$i < 10} {incr i} {
puts $i
}
while
set i 0
while {$i < 10} {
puts [incr 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