A design I like combines a combinator library with an optional facade that gives you a convenient grammar syntax a la a parser generator -- for example, Lua's L

A design I like combines a combinator library with an optional facade that gives you a convenient grammar syntax a la a parser generator -- for example, Lua's LPEG works this way. LPEG is a little awkward imo in how it integrates semantic actions, and I tried to do better in my own library (which unfortunately isn't really ready to share and it's been on the back burner).