On 3/29/21 8:13 AM, Gavin Ray wrote:
> Brief question, is it possible to write this so that the "alias fn" here
> appears as the final argument?
>
> auto my_func(alias fn)(string name, string description, auto
otherthing)
Yes, as a type template parameter but you would have to constrain the
parameter yourself (if you care):
import std.stdio;
import std.traits;
import std.meta;
auto myFunc(F)(string name, F func)
{
// This condition could be a template constraint but they don't
// support error messages.
static assert (is (Parameters!func == AliasSeq!(string)),
"'func' must be a callable that takes 'string'.");
return func(name);
}
void main() {
// One trouble with this "solution" is that for the compiler to
// know the return type of the lambda, the parameter must be
// declared as 'string' (in this case).
writeln(myFunc("foo", (string a) => a ~ '.'));
}
Ali
