How to create delegates with an independent scope?

Vijay Nayar madric at
Wed Mar 30 12:46:07 UTC 2022

Consider the following code example:

import std.stdio;

void main()
   alias DelegateT = string delegate();

   // An array of delegates, each has their own scope.
   DelegateT[] funcs;
   foreach (i; ["ham", "cheese"]) {
     // Deliberately create a copy to keep in delegate scope.
     string myStr = i.dup;
     // The delegate will hopefully carry this copy around in its 
own scope.
     funcs ~= (() => myStr ~ " sandwich");
   foreach (f; funcs) {

The expected output is: "ham sandwich" and then "cheese sandwich".

The actual output is: "cheese sandwich" and then "cheese 

It seems that the variable `myStr` is in a sort of shared scope 
for both functions in the array, and the last value written to it 

How do I create a delegate that acts like a 
[closure](, that is, it carries with it the environment in which it was created?

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