immutable TreeMap cannot be iterated

[ishax-kos]

It appears to be impossible to iterate a tree map that is immutable using a foreach loop. The only option seems to be casting away the immutability.

import std.stdio;
import collections.treemap;


auto func() {
    TreeMap!(string, int) foo;
    foo["foo"] = 1;
    return foo;
}


void main() {
    immutable TreeMap!(string, int) tree = func();

    foreach(k, ref v; tree) { // Try with different iteration variables
        writefln!"%s:%s"(k, v);
    }
}

[ZILtoid1991]

I guess the issue is that the opApply function overrides lack both the const and immutable attributes. I'll try adding them and see if it creates a problem or not, then hopefully publish a new version with the fix.

[ZILtoid1991]

I guess I can add it in the future, but it's not as an easy fix, as modifying the makeFunc functions to generate templates with const and immutable attributes.

One issue is that when I designed this library, I didn't had functional programming in mind. I usually use a mixture of all kinds, using the strength of all various paradigms without overcomplicating things.

Feel free to modify the code if you have the knowledge. Functional programming might even require modifier functions, that add or subtract from the collections by returning a new collection.