Closures/Value capture: Difference between revisions

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=={{header|C++}}==

{{works with|C++11}}

<lang cpp>#include <iostream>

#include <functional>

#include <vector>

int main() {

std::vector<std::function<int()> > funcs;

for (int i = 0; i < 10; i++)

funcs.push_back([=]() { return i * i; });

for ( std::function<int( )> f : funcs )

std::cout << f( ) << std::endl ;

return 0;

}</lang>

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=={{header|EchoLisp}}==

<lang scheme>

(define (fgen i) (lambda () (* i i)))

(define fs (for/vector ((i 10)) (fgen i))) ;; vector of 10 anonymous functions

((vector-ref fs 5)) ;; calls fs[5]

→ 25

</lang>

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=={{header|FreeBASIC}}==

FreeBASIC doesn't support closures or anonymous methods, as such. However, what we can do is to create an array of objects to capture their index and then call a method on those objects which squares the index. This approach is similar to how some other object oriented languages implement closures 'under the hood'.

<lang freebasic>' FB 1.05.0 Win64

Type Closure

Private:

index As Integer

Public:

Declare Constructor(index As Integer = 0)

Declare Function Square As Integer

End Type

Constructor Closure(index As Integer = 0)

This.index = index

End Constructor

Function Closure.Square As Integer

Return index * index

End Function

Dim a(1 To 10) As Closure

' create Closure objects which capture their index

For i As Integer = 1 To 10

a(i) = Closure(i)

Next

' call the Square method on all but the last object

For i As Integer = 1 to 9

Print a(i).Square

Next

Print

Print "Press any key to quit"

Sleep</lang>

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=={{header|Perl 6}}==

{{Works with|Rakudo|2015.12}}

All blocks are anonymous closures in Perl 6, and parameters are lexicals, so it's easy to generate a list of them. We'll use a <tt>gather</tt>/<tt>take</tt> generator loop, and call the closures in random order, just to keep things interesting.

<lang perl6>my @c = gather for ^10 -> $i {

take { $i * $i }

}

.().say for @c.pick(*); # call them in random order</lang>

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Or equivalently, using a more functional notation:

<lang perl6>say .() for pick *, map -> $i { -> {$i * $i} }, ^10</lang>

=={{header|Scala}}==

<lang scala>val closures=for(i <- 0 to 9) yield (()=>i*i)

0 to 8 foreach (i=> println(closures(i)()))

println("---\n"+closures(7)())</lang>

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