Genlex(3o) OCaml library Genlex(3o) NAME Genlex - A generic lexical analyzer. Module Module Genlex Documentation Module Genlex : sig end A generic lexical analyzer. This module implements a simple 'standard' lexical analyzer, presented as a function from character streams to token streams. It implements roughly the lexical conventions of OCaml, but is parameterized by the set of keywords of your language. Example: a lexer suitable for a desk calculator is obtained by let lexer = make_lexer ["+"; "-"; "*"; "/"; "let"; "="; "("; ")"] The associated parser would be a function from token stream to, for in- stance, int , and would have rules such as: let rec parse_expr = parser | [< n1 = parse_atom; n2 = parse_remainder n1 >] -> n2 and parse_atom = parser | [< 'Int n >] -> n | [< 'Kwd "("; n = parse_expr; 'Kwd ")" >] -> n and parse_remainder n1 = parser | [< 'Kwd "+"; n2 = parse_expr >] -> n1 + n2 | [< >] -> n1 One should notice that the use of the parser keyword and associated no- tation for streams are only available through camlp4 extensions. This means that one has to preprocess its sources e. g. by using the "-pp" command-line switch of the compilers. type token = | Kwd of string | Ident of string | Int of int | Float of float | String of string | Char of char The type of tokens. The lexical classes are: Int and Float for integer and floating-point numbers; String for string literals, enclosed in double quotes; Char for character literals, enclosed in single quotes; Ident for identifiers (either sequences of letters, digits, underscores and quotes, or sequences of 'operator characters' such as + , * , etc); and Kwd for keywords (either identifiers or single 'special characters' such as ( , } , etc). val make_lexer : string list -> char Stream.t -> token Stream.t Construct the lexer function. The first argument is the list of key- words. An identifier s is returned as Kwd s if s belongs to this list, and as Ident s otherwise. A special character s is returned as Kwd s if s belongs to this list, and cause a lexical error (exception Stream.Error with the offending lexeme as its parameter) otherwise. Blanks and newlines are skipped. Comments delimited by (* and *) are skipped as well, and can be nested. A Stream.Failure exception is raised if end of stream is unexpectedly reached. OCamldoc 2023-02-12 Genlex(3o)
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