On Thursday, 8 October 2015 at 09:50:12 UTC, John Colvin wrote:
On Thursday, 8 October 2015 at 09:29:30 UTC, tcak wrote:
[...]
I'm 99% sure something like __traits(hasMember, int[], "length"
) should evaluate to true. Please file a bug at
issues.dlang.org I notice it also doesn't work for "ptr".
The correct workaround:
__traits(compiles, A.init.length ));
or
__traits(compiles, listOfStrings.length ));
A.length doesn't work because length is not a static member, so
it's only accessible from an instance.
The __traits(compiles, ...) solution is actually more general
because it will work if .length is implemented via UFCS and
opDispatch.
FYI:
If you want to check whether a statement will compile, as
opposed to an expression, make a function/delegate out of it,
e.g.:
__traits(compiles, { size_t n = A.init.length; });
to check that A has a member length that can be assigned to
size_t.
P.S. always check std.traits for solutions all your static
reflection problems, there's a lot of good stuff in there.
__traits(compiles, { size_t n = A.init.length; }); did the trick.
[code]
size_t maxLength(A)( const A[] listOfString )
if( __traits( compiles, { size_t len = A.init.length; } ) )
{
size_t len = 0;
foreach(A str; listOfString)
if( str.length > len ) len = str.length;
return len;
}
[/code]
BTW, there is nothing like std.traits.hasLength.
