58 lines
1.8 KiB
OCaml
58 lines
1.8 KiB
OCaml
|
(*===----------------------------------------------------------------------===
|
||
|
|
* Lexer
|
||
|
|
*===----------------------------------------------------------------------===*)
|
||
|
|
|
||
|
|
let rec lex = parser
|
||
|
|
(* Skip any whitespace. *)
|
||
|
|
| [< ' (' ' | '\n' | '\r' | '\t'); stream >] -> lex stream
|
||
|
|
|
||
|
|
(* identifier: [a-zA-Z][a-zA-Z0-9] *)
|
||
|
|
| [< ' ('A' .. 'Z' | 'a' .. 'z' as c); stream >] ->
|
||
|
|
let buffer = Buffer.create 1 in
|
||
|
|
Buffer.add_char buffer c;
|
||
|
|
lex_ident buffer stream
|
||
|
|
|
||
|
|
(* number: [0-9.]+ *)
|
||
|
|
| [< ' ('0' .. '9' as c); stream >] ->
|
||
|
|
let buffer = Buffer.create 1 in
|
||
|
|
Buffer.add_char buffer c;
|
||
|
|
lex_number buffer stream
|
||
|
|
|
||
|
|
(* Comment until end of line. *)
|
||
|
|
| [< ' ('#'); stream >] ->
|
||
|
|
lex_comment stream
|
||
|
|
|
||
|
|
(* Otherwise, just return the character as its ascii value. *)
|
||
|
|
| [< 'c; stream >] ->
|
||
|
|
[< 'Token.Kwd c; lex stream >]
|
||
|
|
|
||
|
|
(* end of stream. *)
|
||
|
|
| [< >] -> [< >]
|
||
|
|
|
||
|
|
and lex_number buffer = parser
|
||
|
|
| [< ' ('0' .. '9' | '.' as c); stream >] ->
|
||
|
|
Buffer.add_char buffer c;
|
||
|
|
lex_number buffer stream
|
||
|
|
| [< stream=lex >] ->
|
||
|
|
[< 'Token.Number (float_of_string (Buffer.contents buffer)); stream >]
|
||
|
|
|
||
|
|
and lex_ident buffer = parser
|
||
|
|
| [< ' ('A' .. 'Z' | 'a' .. 'z' | '0' .. '9' as c); stream >] ->
|
||
|
|
Buffer.add_char buffer c;
|
||
|
|
lex_ident buffer stream
|
||
|
|
| [< stream=lex >] ->
|
||
|
|
match Buffer.contents buffer with
|
||
|
|
| "def" -> [< 'Token.Def; stream >]
|
||
|
|
| "extern" -> [< 'Token.Extern; stream >]
|
||
|
|
| "if" -> [< 'Token.If; stream >]
|
||
|
|
| "then" -> [< 'Token.Then; stream >]
|
||
|
|
| "else" -> [< 'Token.Else; stream >]
|
||
|
|
| "for" -> [< 'Token.For; stream >]
|
||
|
|
| "in" -> [< 'Token.In; stream >]
|
||
|
|
| id -> [< 'Token.Ident id; stream >]
|
||
|
|
|
||
|
|
and lex_comment = parser
|
||
|
|
| [< ' ('\n'); stream=lex >] -> stream
|
||
|
|
| [< 'c; e=lex_comment >] -> e
|
||
|
|
| [< >] -> [< >]
|