On Thursday, 29 August 2019 at 08:58:18 UTC, Mek101 wrote:
As the title says, is there a way to test the return type of
the 'unaryFun' and 'binaryFun' templates from 'std.functional'?
I have the following code, and I want to to be sure that
'predicate' returns a boolean, but neither
'is(typeof(predicate) == bool)' or 'is(ReturnType!predicate ==
bool)' seem to work.
private alias NullSized = Nullable!(size_t, size_t.max);
public NullSized indexOf(alias pred = "a == b", Range, V)(Range
array, V value)
if((isRandomAccessRange!Range || isStaticArray!Range))
{
alias predicate = binaryFun!pred;
for(size_t i = 0; i < array.length; i++)
if(predicate(array[i], value))
return NullSized(i);
return NullSized.init;
}
You'll need to test calling the predicate with the actual types
it will be processing - something like
is(typeof(predicate(array[0], value)) == bool). You could (and
quite possibly should) do this in the template constraint.
The reason is binaryFun actually returns a generic function - a
template that needs to know its actual argument types. For fun,
you could actually test is(typeof(predicate!(ElementType!Range,
V)) == bool).
--
Simen
