Quex - Example

Example

Quex follows the syntax of the classical tools lex and flex for the description of regular expressions. The example in the section Flex can be translated into Quex source code as follows:

header { #include // C++ version of 'stdlib.h' } define { digit letter } mode X : { "+" => QUEX_TKN_PLUS; "-" => QUEX_TKN_MINUS; "*" => QUEX_TKN_TIMES; "/" => QUEX_TKN_SLASH; "(" => QUEX_TKN_LPAREN; ")" => QUEX_TKN_RPAREN; ";" => QUEX_TKN_SEMICOLON; "," => QUEX_TKN_COMMA; "." => QUEX_TKN_PERIOD; ":=" => QUEX_TKN_BECOMES; "=" => QUEX_TKN_EQL; "<>" => QUEX_TKN_NEQ; "<" => QUEX_TKN_LSS; ">" => QUEX_TKN_GTR; "<=" => QUEX_TKN_LEQ; ">=" => QUEX_TKN_GEQ; "begin" => QUEX_TKN_BEGINSYM; "call" => QUEX_TKN_CALLSYM; "const" => QUEX_TKN_CONSTSYM; "do" => QUEX_TKN_DOSYM; "end" => QUEX_TKN_ENDSYM; "if" => QUEX_TKN_IFSYM; "odd" => QUEX_TKN_ODDSYM; "procedure" => QUEX_TKN_PROCSYM; "then" => QUEX_TKN_THENSYM; "var" => QUEX_TKN_VARSYM; "while" => QUEX_TKN_WHILESYM; {letter}({letter}|{digit})* => QUEX_TKN_IDENT(strdup(Lexeme)); {digit}+ => QUEX_TKN_NUMBER(atoi(Lexeme)); . => QUEX_TKN_UNKNOWN(Lexeme); }

The brief token senders via the "=>" operator set the token ID of a token object with the token ID which follows the operator. The arguments following inside brackets are used to set contents of the token object. Note, that skipping whitespace can be achieved via skippers which are optimized to pass specific character sets quickly (see the "" tag). For more sophisticated token actions C-code sections can be provided, such as

... {digit}+ { if( is_prime_number(Lexeme) ) ++prime_number_counter; if( is_fibonacci_number(Lexeme) ) ++fibonacci_number_counter; self.send(QUEX_TKN_NUMBER(atoi(Lexeme))); } ...

which might be used to do some statistics about the numbers which occur in analyzed code.

Famous quotes containing the word example:

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