Scala's Parser-Combinators are about as good as you are going to get http://www.scala-blogs.org/2009/04/combinators-for-pretty-printers-part-1.html http://www.s

Scala's Parser-Combinators are about as good as you are going to get http://www.scala-blogs.org/2009/04/combinators-for-pretty-printers-part-1.html http://www.scala-blogs.org/2009/04/combinators-for-pretty-pr.... Consider the grammar for simple math expressions: expr ::= sum sum ::= product { ("+" | "-") product } product ::= power { ("*" | "/") power } power ::= factor [ "^" factor ] factor ::= "(" expr ")" | variable | constant variable ::= identifier constant ::= floatLiteral It's pure-Scala is def expr = sum def sum = product ~ rep(("+" | "-") ~ product) def product = power ~ rep(("*" | "/") ~ power) def power = factor ~ opt("^" ~ factor) def factor = "(" ~ expr ~ ")" | variable | constant def variable = ident def constant = floatLit And since it's pure-Scala, you get all the benefit of static typing (error detection, auto-complete, etc) when writing your parser. There's also no extra compile step: your parser compiles with the rest of your program and is just a java Object with a parseAll() method. Lastly, it's a superset of PEG, which means that its behavior and limitations are all pretty well-studied academically and well-defined (which is more than can be said of most hacked-together regex solutions!). Pyparsing is pretty cool as well, for python, but it's somewhat more verbose since python isn't as DSL-friendly as scala: http://pyparsing.wikispaces.com/HowToUsePyparsing http://pyparsing.wikispaces.com/HowToUsePyparsing EDIT: a (different) example from Pyparsing: integer = Word( nums ) variable = Word( alphas, max=1 ) arithOp = Word( "+-*/", max=1 ) equation = variable + "=" + integer + arithOp + integer As far as I can tell, Pyparsing is also a superset of PEG.