On Fri, Aug 30, 2013 at 11:51:37PM +0200, bearophile wrote:
> Joseph Rushton Wakeling:
>
> > static if (!__traits(hasMember, G, "directed") ||
> > !__traits(hasMember, G, "edge") ||
> > !__traits(hasMember, G, "edgeCount") ||
> > !__traits(hasMember, G, "vertexCount") ||
> > !__traits(hasMember, G, "isEdge") ||
> > !__traits(hasMember, G, "edgeID") ||
> > !__traits(hasMember, G, "addEdge") ||
> > !__traits(hasMember, G, "degreeIn") ||
> > !__traits(hasMember, G, "degreeOut") ||
> > !__traits(hasMember, G, "incidentEdgesIn") ||
> > !__traits(hasMember, G, "incidentEdgesOut") ||
> > !__traits(hasMember, G, "neighboursIn") ||
> > !__traits(hasMember, G, "neighboursOut"))
>
> Perhaps can shorten that code writing a hasMembers helper (and I
> suggest to keep those names sorted):
[...]
Here's a first stab at a possible implementation:
/* Warning: untested code */
import std.typetuple : allSatisfy;
template isString(T) {
// There may already be something in Phobos that does
// this, but I'm too lazy to look.
enum isString = is(T == string);
}
template hasMembers(alias T, Members...)
if (allSatisfy!isString(Members))
{
// Template recursion + exprTuple slicing FTW :)
enum hasMembers = __traits(hasMember, T, Members[0]) &&
hasMembers!(T, Members[1..$]);
}
void myFunc(G)(G graph)
{
static if (hasMembers!(G, "directed", "edge", /* ... */))
{
...
}
}
T
--
Computers shouldn't beep through the keyhole.
