On Saturday, 25 June 2016 at 08:46:05 UTC, John wrote:
Writing a long series of "static if ... else" statements can be
tedious and I'm prone to leaving out the crucial "static" after
"else", so I was wondered if it was possible to write a
template that would resemble the switch statement, but for
types.
Closest I came up to was this:
void match(T, Fs...)() {
foreach (F; Fs) {
static if (isFunctionPointer!F) {
alias Ps = Parameters!F;
static if (Ps.length == 1) {
static if (is(Ps[0] == T)) F(Ps[0].init);
}
}
}
}
void test(T)(T t) {
match!(T,
(int _) => writeln("Matched int"),
(string _) => writeln("Matched string")
);
}
But that's pretty limited and I'd like to be able to match on
whether a type derives from T as well. I just can't figure it
out.
Something like this would be ideal...
match!(T,
int => writeln("Matched int"),
is(T : SomeObject) => writeln("Derives from SomeObject")
);
Anyone able to improve on it?
Instead of passing functions to match!, pass pairs of arguments,
like this:
match!(T,
int, writeln("Matched int"),
is(T : SomeObject), writeln("Derives from SomeObject");
);
Now, in the implementation, foreach pair of arguments, if the
first member is a type that matches your target, perform that
branch; otherwise, if the first member is a boolean value, and it
is true, perform the branch.
