On Mon, Aug 02, 2021 at 02:31:45PM +0000, Rekel via Digitalmars-d-learn wrote:
> I recently found one can return function calls to void functions, though I don't remember any documentation mentioning this even though it doesn't seem trivial.

This is intentional, in order to make it easier to write generic code without always having to special-case functions that don't return anything. E.g.:

	auto myWrapper(alias func, Args...)(Args args) {
		// Don't have to special case void return.
		return func(args);
	}

	int hooray(int i) { return i+1; }
	void boo(int j) { return; }

	int z = myWrapper!hooray(1);
	myWrapper!boo(2);

Otherwise you'd have to litter your code with redundant special cases:

	auto myWrapper(alias func, Args...)(Args args) {
		static if (is(ReturnType!func == void))
			func(args);
		else
			return func(args); // same thing but different
	}

Allowing `return func(args)` for void functions eliminates the need for
such special cases.


T

-- 
"640K ought to be enough" -- Bill G. (allegedly), 1984. "The Internet is not a primary goal for PC usage" -- Bill G., 1995. "Linux has no impact on Microsoft's strategy" -- Bill G., 1999.

On Monday, 2 August 2021 at 14:51:07 UTC, H. S. Teoh wrote:
> This is intentional, in order to make it easier to write generic code without always having to special-case functions that don't return anything.

Ooh that indeed seems useful. Thanks for the hint.
Also slightly off topic, but when would one use an alias instead of a function/delegate? I haven't used aliases before.

On 8/2/21 9:42 AM, Rekel wrote:

> when would one use an alias instead of a
> function/delegate? I haven't used aliases before.

alias will match both functions and delegates... and... any symbol at all. So, if you don't have a reason to constain the user, callable template parameters are most usefully aliases.

Ali

On Mon, Aug 02, 2021 at 04:42:14PM +0000, Rekel via Digitalmars-d-learn wrote: [...]
> Also slightly off topic, but when would one use an alias instead of a function/delegate? I haven't used aliases before.

When you want a compile-time binding that could potentially elide the indirect function call to a delegate.

	// This generates a specialized template instance with
	// `callback` bound to the passed-in compile-time argument, for
	// each call to `myFunc`.
	auto myFunc(alias callback)(...) { ...  }

	// This is a single common function that receives an opaque
	// runtime delegate and binds it at runtime.
	auto myFunc(int delegate(...) callback, ...) { ...  }


T

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