Functional LL(x) parsing with monadic combinators.
This module implements functional left-shift/left-reduce parser combinators using a state-exception monad over a sequence of input symbols. The input symbol sequence is the state, and the recognized production is either a returned value Some v, or None if the input stream is not recognized. Composing a grammar production from a sequence of other productions is done by using the bind operator. Backtracking assumes the input stream is confluently persistent.
The input is conceptually sequence of symbol value, attributed in the iota type with stream position. Accordingly, productions are returned wrapped in a 'a form type that conceptually represents the value and the span of positions where it was recognized in the input. However, a simplified module signature is provided where type iota = symbol and type 'a form = 'a.
Syntax errors can be raised with arbitrary OCaml exceptions. Exceptions can be caught, and various functions are available for error recovery.
module type Form = sig ... endDefine a module of this type in a scanner basis. It defines the functions required by the basic scanner to relate produced values and their corresponding 'a form.
module type Basis = sig ... endDefine a module of this type as the basis of a scanner.
module type Profile = sig ... endThe signature of a basic scanner. Note Well: names are short to economize on souce code size in writing grammars by hand.
module Create
(B : Basis) :
Profile
with type symbol := B.Symbol.t
and type 'a form := 'a B.Form.t
and type position := B.positionUse Create(B) to create a basic scanner on the basis of B.
module Simple : sig ... endmodule Staging : sig ... endmodule ASCII : sig ... endThis module provides simple scanners for analyzing texts encoded in 8bit-extended ASCII text encodings, e.g. ISO 8859 Latin, without any concept of stream position.