Yet another const problem...

[Steven Schveighoffer]

On Sun, 20 May 2012 20:07:04 -0400, Mehrdad <wfunction at hotmail.com> wrote:

> struct Foo
> {
> 	@property bool empty() const { return p == null; }
> 	@property auto front() inout { return p; }
> 	void popFront() { p--; }
>
>
> 	// So far so good? okay, let's define save()..
>
> 	auto save() inout { return typeof(this)(this.tupleof); }
>
>
> 	// Now let's implement opApply() using the above ^^
>
> 	int opApply(void delegate(size_t, typeof(p)) dg) const
> 	{
> 		size_t i = 0;
> 		int r = 0;
>
> 		// So far so good...
> 		for (auto me = this.save(); !r && !me.empty; me.popFront())
> 		{
> 			// Whoops, won't work -- 'me' is const! :(
> 			r = dg(me);
> 		}
>
> 		return r;
> 	}
> }
>
>
>
> How do you fix this without duplicating your code?

This is yet another cry for tail-const.

It's very obvious we need a clean solution for tail-const before the const  
story is finished.

The answer for now?  Don't make opApply const.

-Steve