Foreach As Loop
Contents |
Foreach As
Description
Loop based on an expression.
foreach( <expression> as <value> )
{
statements
...
}
foreach( <expression> as <value> from <offset> )
{
statements
...
}
foreach( <expression> as <value> from <start> to <end> )
{
statements
...
}
Parameters
expression
An expression to use could equal an array, string, whatever.
value
The value to place the result in most common as a $variable.
Remarks
Foreach...As statements may be nested.
If the expression contains an array the loop will cycle through each element in the array.
If the expression contains a string or numbers it will cycle through each char.
It is a bad idea to try edit the array while you are loop through it... Strange things may happen including hard crashes.
Example
Are you trying use a Foreach on a string but getting Char data type when you want String for each char then see this example
// Define a string $str = "Hello"; // Loop through the string as chars // notice each one is a char data type // this might cause problems if you expect // to use it as a string see below for solution foreach($str as my $c) { echo vardump($c); } // Prints // char'H' // char'e' // char'l' // char'l' // char'o' // Solution? Cast to string foreach($str as my $c) { $c = (string)$c; echo vardump($c); } // Prints // string(1) "H" // string(1) "e" // string(1) "l" // string(1) "l" // string(1) "o"
Using from
$a = array("Zero", "One", "Two", "Three", "Four", "Five", "Six"); foreach($a as $c from 1) { say $c; } // Prints // One // Two // Three // Four // Five // Six
Using from and to
$a = array("Zero", "One", "Two", "Three", "Four", "Five", "Six"); foreach($a as $c from 1 to 3) { say $c; } // Prints // One // Two // Three
Here we cycle through binary data :
$binary = Pack("ifz0", (int)100, (float)777.42, "Hello"); foreach( $binary as $item ) { println( "Index '" . DecPad($item, 3) . "' " . "Dec '$item' " . "Hex '" . Hex($item) . "' " . "Char '" . Chr($item) . "'" ); }
Here we cycle through an array :
$arr = array( 2, 4, 6, 8, 10 ); foreach( $arr as $item ) { println("Value is $item"); }
Here we cycle through each char in a string :
$arr = "Hello World"; foreach( $arr as $item ) { println("Value is $item"); }
Here we cycle through each letter in a float :
$arr = 777.42; foreach( $arr as $item ) { println("Value is $item"); }
You can also referance when using arrays using the pointer & operator for example :
$arr = array( 2, 4, 6, 8, 10 ); foreach( $arr as & $item ) { println("Value is $item"); // Prints 2 4 6 8 10 *$item *= 2; // notice the * before $item? this tells Sputnik // to resolve the Pointer and get the real value // then we can modify it } println(""); foreach( $arr as $item ) { println("Value is $item"); // Prints 4 8 12 16 20 }
See the & before $item on the first loop? This causes $item to actually LINK to the real element inside the array so changing $item will change the item in the array.
This can be seen by printing the array after changing it in the example.
Note - You can only change elements in an array! This will not work with anything else.
A reverse foreach
println("Value $i") foreach("Hello world" as $i);
Example of unpacking nested arrays with list()
$array = array( array(1, 2), array(3, 4) ); foreach ($array as list($a, $b)) { // $a contains the first element of the nested array, // and $b contains the second element. echo "A: $a; B: $b\n"; } // Prints // A: 1; B: 2 // A: 3; B: 4
Another example of unpacking nested arrays with list()
$array = array( array(1, 2, 3, 4), array(5, 6, 7, 8) ); foreach ($array as list($a, $b, $c, $d)) { // $a contains the first element of the nested array, // and $b contains the second element. echo "A: $a; B: $b; C: $c; D: $d\n"; } // Prints // A: 1; B: 2; C: 3; D: 4 // A: 5; B: 6; C: 7; D: 8
Yet another example of unpacking nested arrays with list() however this one only works if there is only 1 element in each array (key, value) and it must be a hash and not numeric (like normal arrays)
$array = array( array("Cat" => "Meow"), array("Dog" => "Woof"), array("Foo" => "Bar") ); foreach ($array as list($key, *$value)) { // $a contains the first element of the nested array, // and $b contains the second element. echo "Key: $key | Value: $value\n"; } // Prints // Key: Cat | Value: Meow // Key: Dog | Value: Woof // Key: Foo | Value: Bar
Looping a .NET array
use("System"); $chars = %Char[]->new(3); $chars[0] = 'A'; $chars[1] = 'B'; $chars[2] = 'C'; say "Printing"; foreach($chars as $c) { say $c; } // Printing // A // B // C
Looping a .NET array as a ref to modify its values in real time
use("System"); $chars = %Char[]->new(3); $chars[0] = 'A'; $chars[1] = 'B'; $chars[2] = 'C'; say "Printing"; foreach($chars as &$c) { say $c; *$c = 'T'; } say "Printing modified array"; foreach($chars as $c) { say $c; } // Printing // {REF}:A // {REF}:B // {REF}:C // Printing modified array // T // T // T
Same as above
use("System"); $chars = %Char[]->new(3); $chars[0] = 'A'; $chars[1] = 'B'; $chars[2] = 'C'; say "Printing"; foreach($chars as &$c) { say $c; *$c = AscW(*$c) + 10; } say "Printing modified array"; foreach($chars as $c) { say $c; } // Printing // {REF}:A // {REF}:B // {REF}:C // Printing modified array // K // L // M
Loop through a string and print each char but do it with a ref so we can modify the string in place
$str = "Hello"; say "Printing string"; foreach($str as &$c) { say $c; *$c = AscW(*$c) + 10; } say "Printing modified string"; foreach($str as $c) { say $c; }
Example of using List() with an array that contains no nested arrays
$a = array("One", "Two", "Three", "Four", "Five", "Six"); foreach($a as list($k, $j)) { say "$k - $j"; } // Prints // One - Two // Three - Four // Five - Six
Same as above but more arguments to extract
$a = array("One", "Two", "Three", "Four", "Five", "Six"); foreach($a as list($k, $j, $l)) { say "$k - $j - $l"; } // Prints // One - Two - Three // Four - Five - Six
Of course unpacking only one argument is the same as a normal foreach
$a = array("One", "Two", "Three", "Four", "Five", "Six"); foreach($a as list($k)) { say "$k"; } // Prints // One // Two // Three // Four // Five // Six
Example of using List() with a .NET array
use("System"); $strs = %String[]->new(8); $strs[0] = "One"; $strs[1] = "Two"; $strs[2] = "Three"; $strs[3] = "Four"; $strs[4] = "Five"; $strs[5] = "Six"; $strs[6] = "Seven"; $strs[7] = "Eight"; foreach($strs as list($k, $j)) { say "$k - $j"; } // Prints // One - Two // Three - Four // Five - Six // Seven - Eight
