On Thursday, 18 May 2017 at 22:31:47 UTC, Stefan Koch wrote:
Granted this version will result in undefined behavior if you
pass something like (cast(ET) 3) to it.
But the 55x increase in compilation speed is well worth it :)
This code will replicate to!string behavior perfectly but will
only take 30 milliseconds to compile:
string enumToString(E)(E v)
{
static assert(is(E == enum), "emumToString is only meant for
enums");
mixin({
string result = "switch(v) {\n";
foreach(m;[__traits(allMembers, E)])
{
result ~= "\tcase E." ~ m ~ " :\n"
~ "\t\treturn \"" ~ m ~ "\";\n";
}
result ~= "\tdefault: break;\n";
result ~= "}\n";
enum headLength = E.stringof.length + "cast()".length;
result ~= `
enum headLength = ` ~ headLength.stringof ~ `;
uint val = v;
char[` ~ (headLength + 10).stringof ~ `] res = "cast(` ~
E.stringof ~ `)";
uint log10Val = (val < 10) ? 0 : (val < 100) ? 1 : (val <
1000) ? 2 : (val < 10000) ? 3
: (val < 100000) ? 4 : (val < 1000000) ? 5 : (val <
10000000) ? 6
: (val < 100000000) ? 7 : (val < 1000000000) ? 8 : 9;
foreach(i;0 .. log10Val + 1)
{
res[headLength + log10Val - i] = cast(char) ('0' + (val %
10));
val /= 10;
}
return res[0 .. headLength + log10Val + 1].idup;
`;
return result;
} ());
}
