On Saturday, 25 June 2016 at 08:46:05 UTC, John wrote:
Anyone able to improve on it?
q&d hack:
template tyma(T, Cases...) {
import std.traits;
template GetFunc(size_t idx) {
static if (idx >= Cases.length) {
static assert(0, "no delegate for match");
} else static if (isCallable!(Cases[idx])) {
enum GetFunc = Cases[idx];
} else {
enum GetFunc = GetFunc!(idx+1);
}
}
template Matcher(size_t idx) {
//pragma(msg, "T=", T, "; idx=", idx, "; Cases[idx]=",
Cases[idx], "; is=", is(typeof(T) == Cases[idx]));
static if (idx >= Cases.length) {
static assert(0, "no match, consider adding `void` branch");
} else static if (isCallable!(Cases[idx])) {
enum Matcher = Matcher!(idx+1);
} else static if (is(Cases[idx] == void)) {
enum Matcher = GetFunc!(idx+1);
} else static if (is(typeof(Cases[idx]) == string)) {
mixin("static if (is(T:"~Cases[idx]~")) enum Matcher =
GetFunc!(idx+1); else enum Matcher = Matcher!(idx+1);");
} else static if (is(typeof(Cases[idx]))) {
static assert(0, "unexpected something in cases:
"~Cases[idx].stringof);
} else static if (is(T == Cases[idx])) {
enum Matcher = GetFunc!(idx+1);
} else {
enum Matcher = Matcher!(idx+1);
}
}
enum tyma = Matcher!0;
}
void main () {
import std.stdio;
auto res = tyma!(int,
string, () => "string",
"long", () => "integral",
void, () => "anything",
)();
writeln(res);
}
note that you should separate type names from labdas with ","
instead of doing `int => "integral`, and have to add `()` at the
end to actually call the delegate.
