TeXのDSL的ななにか

texdsl.d

import std.array;
import std.ascii;
import std.format;
import std.stdio;
import std.string;


void main()
{
    auto fig =
        TeX.Figure(["!t"], TeX.Center(TeX
            .includegraphics(["width=65mm"], "fig/foo.pdf").br
            .caption("なんかの図")
            .label("fig:foo")
        ));

    writeln(fig);
}


struct TeX 
{
  static:
    TeXValue opDispatch(string name)(string arg) { return opDispatch!name(null, arg); }

    TeXValue opDispatch(string name)(string[] opt, string arg)
    {
        auto app = appender!string();
        auto sub = appender!string();

        if(opt.length)
            sub.formattedWrite(`[%-(%s, %)]`, opt);

        if(name[0].isUpper)
        {
            app.formattedWrite(`\begin%1$s{%2$s}%3$s\end{%2$s}`, sub.data, name.toLower, arg);
        }
        else
        {
            app.formattedWrite(`\%1$s%2$s{%3$s}`, name, sub.data, arg);
        }

        return TeXValue(app.data);
    }
}


struct TeXValue
{
    this(string str)
    {
        _str = str;
    }


    string toString() const pure nothrow @safe @nogc @property { return _str; }
    alias toString this;

  const:
    TeXValue opDispatch(string name)(string arg) { return opDispatch!name(null, arg); }

    TeXValue opDispatch(string name)(string[] opt, string arg)
    if(isLower(name[0]))
    {
        auto app = appender!string();
        auto sub = appender!string();

        if(opt.length)
            sub.formattedWrite(`[%-(%s, %)]`, opt);

        app.put(_str);
        app.put(`\n`);

        switch(name)
        {
          default:
            app.formattedWrite(`\%1$s%2$s{%3$s}`, name, sub.data, arg);
        }

        return TeXValue(app.data);
    }


    TeXValue opDispatch(string name)() @property
    {
        auto app = appender!string();
        app.put(_str);

        switch(name)
        {
          case "br":
            app.put(`\\ `);

          default:
            app.formattedWrite(`\%1$s`, name);
        }

        return TeXValue(app.data);
    }

  private:
    string _str;
}