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