Re: Converting a type to a char

[Paul Backus via Digitalmars-d-learn]

On Friday, 25 January 2019 at 15:53:10 UTC, Thomas Gregory wrote:

I would like to check that a char (unknown at compile time) matches a particular type but I would like to do so without if statements or a hash map as I would like it to be as fast as possible.

Ideally I would choose something like this:

enum typeIndex{
byte = 0,
ubyte,
short,
ushort,
int,
uint
}

char[6] typechars="cCsSiI";

bool check(T)(char c){
   return typechars[typeIndex(typeof(T))]==c;
}

Though I know this is implementation is not remotely correct D.

You can do this with AliasSeq and staticIndexOf:

import std.meta;

alias Types = AliasSeq!(byte, ubyte, short, ushort, int, uint);
enum typeIndex(T) = staticIndexOf!(T, Types);
char[6] typechars="cCsSiI";

bool check(T)(char c) {
    return typechars[typeIndex!T] == c;
}

Runnable version: https://run.dlang.io/is/Tps38K