Sometimes closures are kind of different....

capture.cpp

#include "stdafx.h"
#include <stdio.h>

int _tmain(int argc, _TCHAR* argv[])
{
	auto banana = 1;
	auto func1 = [banana](int i) -> int { return i + banana; };
	banana  = 5;

	auto result = func1(3);
	printf("result is %d\n", result); // prints 4

	return 0;
}

capture.cs

var banana = 1;
Func<int, int> func1 = x => { return x + banana; };
banana = 2;
var result = func1(3);
Console.WriteLine(result); // returns 5

capture.py

banana  = 1
func1 = lambda x: x + banana
banana = 2
result = func1(3)
print result # prints 5

capture1.m

#import <Foundation/Foundation.h>

int main(int argc, const char *argv[]) {
	@autoreleasepool {
		int banana = 1;
		int (^func)(int) = ^int(int x) {
			return x + banana;
		};
		banana = 2;
		int result = func(3);
		NSLog(@"%d", result); // prints 4
	}
	return 0;
}

capture1.php

<?
$banana = 1;
$greet = function($x) use ($banana) { 
    return $x + $banana; };
$banana = 2;
$result = $greet(3);
echo $result; // prints 4

capture2.cpp

#include "stdafx.h"
#include <stdio.h>
 
int _tmain(int argc, _TCHAR* argv[])
{
	auto banana = 1;
	auto func1 = [&banana](int i) -> int { return i + banana; };
	banana  = 5;
 
	auto result = func1(3);
	printf("result is %d\n", result); // prints 8!!!
 
	return 0;
}

capture2.m

#import <Foundation/Foundation.h>

int main(int argc, const char *argv[]) {
	@autoreleasepool {
		__block int banana = 1;
		int (^func)(int) = ^int(int x) {
			return x + banana;
		};
		banana = 2;
		int result = func(3);
		NSLog(@"%d", result); // prints 5
	}
	return 0;
}

capture2.php

<?
$banana = 1;
$greet = function($x) use (&$banana) { 
    return $x + $banana; };
$banana = 2;
$result = $greet(3);
echo $result; // prints 5

JavaScript, ES6 style:

var banana = 1;

var fn = x => x + banana;

banana = 2;

console.log(fn(3));

#include "stdafx.h"
#include <stdio.h>

int _tmain(int argc, _TCHAR* argv[])
{
    auto banana = 1;
    auto func1 = [&banana](int i) -> int { return i + banana; };
    banana  = 5;

    auto result = func1(3);
    printf("result is %d\n", result); // prints 8

    return 0;
}

@Hdesai you can use the backtick to set the code block so you get proper formatting :)

@aaronpowell. Thanks! done.

@Hdesai

If you take a look it actually returns 8 and not 4, why? because "banana" is capture by reference and not by copy (the default behaviour).

Oh!

This is what your nice compiler generates:

using System;
using System.Runtime.CompilerServices;

namespace ConsoleApplication2
{
  internal class Program
  {
    public Program()
    {
      base.\u002Ector();
    }

    private static void Main(string[] args)
    {
      Program.\u003C\u003Ec__DisplayClass1 cDisplayClass1 = new Program.\u003C\u003Ec__DisplayClass1();
      cDisplayClass1.banana = 1;
      // ISSUE: method pointer
      Func<int, int> func = new Func<int, int>((object) cDisplayClass1, __methodptr(\u003CMain\u003Eb__0));
      cDisplayClass1.banana = 2;
      Console.WriteLine(func(3));
    }

    [CompilerGenerated]
    private sealed class \u003C\u003Ec__DisplayClass1
    {
      public int banana;

      public \u003C\u003Ec__DisplayClass1()
      {
        base.\u002Ector();
      }

      public int \u003CMain\u003Eb__0(int x)
      {
        return x + this.banana;
      }
    }
  }
}

See? now it's clear :)