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Debian 7.3.0(Wheezy) |
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Genlex(3o) |
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Genlex − A generic lexical analyzer.
Module Genlex
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 Caml, 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 instance, int , and would have rules such as:
let parse_expr = parser [< ’Int n >] −> n | [< ’Kwd ( ; n = parse_expr; ’Kwd ) >] −> n | [< n1 = parse_expr; n2 = parse_remainder n1 >] −> n2 and parse_remainder n1 = parser [< ’Kwd + ; n2 = parse_expr >] −> n1+n2 | ...
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 keywords. 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 Parse_error ) otherwise. Blanks and newlines are skipped. Comments delimited by (* and *) are skipped as well, and can be nested.
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Genlex(3o) | |