The tool fslex.exe is a standard lexer-generator along the lines of flex and ocamllex. The input specifies a set of finite state machines that consume ASCII input, recognizing the longest possible match according to a set of regular expressions, consuming this input and evaluating a corresponding expression, which may in turn involve a transition to another state and recursive invocations of the lexical analysis engine.

The notes on the F# Wiki are currently the best place to go for information on fslex.

The tool fsyacc.exe is a LALR parser generator. It follows essentially the same specification as the 'oamlyacc' parser generator, especially when used with the --ml-compatibility switch.

The notes on the F# Wiki are currently the best place to go for information on fsyacc.