d串插值与串插件

原文

import std.stdio;
import std.string;
import std.array;
import std.range.primitives;

string mwrite(string str) @safe pure {
    size_t istart;
    bool inword = false;
    auto result = appender!(string[]);
    auto vars = appender!(string[]);
    foreach (i, dchar c; str) {
        if (!inword) {
            if (c == '{') {
                result.put(str[istart .. i]);
                istart = i+1;
                inword = true;
            }
        } else {
            if (c == '}') {
                result.put("%s");
                vars.put(str[istart .. i]);
                istart = i+1;
                inword = false;
            }
        }
    }
    if (!inword && istart < str.length)
        put(result, str[istart .. $]);

    return format!`writef("%s", %s);`(result.data.join, vars.data.join(`, `));
}
string mwriteln(string str) @safe pure {
    string result = mwrite(str);
    enum toReplace = "writef(";
    return "writefln(" ~ result[toReplace.length .. $];
}

void main() {
    int x = 4;
    float y = 3.5;
    mixin(mwriteln(`X:{x} Y:{y}`));
    mixin(mwriteln(`Which is larger? {x>y?"X":"Y"}`));
}