The original Lex Language Project produced tools that were proprietary to AT&T Unix. In the 1990s, the open-source community developed (Fast Lexical Analyzer Generator) as a free alternative. Flex generates C code that is significantly faster than the original Lex—often 20-50% faster—and supports more advanced features:
"" return OPEN_BRACE; "" return CLOSE_BRACE; "[" return OPEN_BRACKET; "]" return CLOSE_BRACKET; ":" return COLON; "," return COMMA; "true" return BOOLEAN; "false" return BOOLEAN; "null" return NULL_TOKEN; \"([^\\\"]|\\.)*\" return STRING; -?[0-9]+(\.[0-9]+)? return NUMBER; [ \t\n]+ /* skip whitespace */ . return INVALID; lex language project
Most industrial compilers (including the original gcc and clang in their early stages) used the Lex/Yacc (or Flex/Bison) combination. Even today, the interface between Lex and Yacc—via the yylval union—remains a canonical example of modular design. The original Lex Language Project produced tools that
Lex is , but less expressive than Interlingua. It is more practical than Toki Pona (which has only 120 words) but less proven . return NUMBER; [ \t\n]+ /* skip whitespace */
