Playing arround with mixin - alias?

[ketmar via Digitalmars-d-learn]

Martin Tschierschke wrote:

>> i doubt so.
> So my "solution" on how to get a short cut for using:
>
> writeln(mixin(interp!"${name} you are app. ${age*365} days old"));
..

NEVER. EVER. USE. THE. FOLOWING. IN. YOUR. CODE.
NEVER!!!


import std.stdio;

mixin template usesexpand() {
	import std.format : format;
	string sexpand1(string s) () {
		char[] res;
		res.length = s.length+1024;
		auto rused = res.length;
		auto rpos = rused*0; // i really HAET `size_t`!
		void put(bool escape=true) (const(char)[] s...) {
			foreach (char ch; s) {
				static if (escape) {
					if (ch == '"' || ch == '\\') {
						if (rpos == rused) { rused += 1024; res.length = rused; }
						res[rpos++] = '\\';
					}
				}
				if (rpos == rused) { rused += 1024; res.length = rused; }
				res[rpos++] = ch;
			}
		}

		char[] fmt;
		fmt.length = 256;
		auto fused = fmt.length;
		auto fpos = fused*0; // i really HAET `size_t`!
		void putfmt (const(char)[] s...) {
			foreach (char ch; s) {
				if (fpos == fused) { fused += 1024; fmt.length = fused; }
				fmt[fpos++] = ch;
			}
		}

		putfmt(`format("`);

		auto pos = rpos, epos = rpos;
		pos = 0;
		while (pos < s.length) {
			epos = pos;
			while (epos < s.length && s[epos] != '$') ++epos;
			putfmt("%s");
			put!false(`, "`);
			if (epos+1 >= s.length || s[epos+1] != '{') {
				put(s[pos..epos+1]);
				put!false(`"`);
				pos = epos+1;
				continue;
			}
			put(s[pos..epos]);
			put!false(`"`);
			pos = epos+2;
			while (epos < s.length && s[epos] != '}') ++epos;
			if (epos > pos) {
				putfmt("%s");
				put(`, `);
				put(s[pos..epos]);
			}
			pos = epos+1;
		}
		put(`)`);
		putfmt(`"`);
		return cast(string)fmt[0..fpos]~cast(string)res[0..rpos]; // it is safe to cast here
	}
	enum sexpandstr(string s) = sexpand1!s;
	enum sexpand(string s) = mixin(sexpand1!s);
	void echo(string s) () { writeln(mixin(sexpand1!s)); }
}

mixin usesexpand;
immutable n = 40;

enum nstr = sexpand!"n is ${n+2}";

void main () {
	mixin usesexpand;
	int a = 42/2;
	echo!"a is ${a*2}"; //writeln(mixin(sexpandstr!"a is ${a*2}"));
	writeln(nstr);
}