Flex Lexer and Parser for C++: A Compilation Overview, Slides of Compiler Construction

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Lecture 10

Using Generated ScannerUsing Generated ScannerUsing Generated ScannerUsing Generated Scanner

void main()

FlexLexer lex;

int tc = lex.yylex();

while(tc != 0)

cout << tc << “,”

<<lex.YYText() << endl;

tc = lex.yylex();

Input TokenizedInput TokenizedInput TokenizedInput Tokenized

258,tc

258,lex

258,yylex

263,while

Input TokenizedInput TokenizedInput TokenizedInput Tokenized

258,tc

258,cout

258,tc

Input TokenizedInput TokenizedInput TokenizedInput Tokenized

258,endl 290,; 258,tc 266,= 258,lex 291,. 258,yylex 283,( 284,) 290,; 286,}

Flex Input for C++Flex Input for C++Flex Input for C++Flex Input for C++

• ISO C++ lexical analyzer.
• Based on the ISO C++ draft standard of December '96. */ %{ #include <ctype.h> #include <stdio.h> #include “tokdefs.h" int lineno; static int yywrap(void); static void skip_until_eol(void); static void skip_comment(void); static int check_identifier(const char *); %}

"\n" { ++lineno; } [\t\f\v\r ]+ { /* Ignore whitespace. / } "/" { skip_comment(); } "//" { skip_until_eol(); } "{" { return '{'; } "<%" { return '{'; } "}" { return '}'; } "%>" { return '}'; } "[" { return '['; } "<:" { return '['; }

"]" { return ']'; } ":>" { return ']'; } "(" { return '('; } ")" { return ')'; } ";" { return ';'; } ":" { return ':'; } "..." { return ELLIPSIS; } "?" { return '?'; } "::" { return COLONCOLON; } "." { return '.'; } "." { return DOTSTAR; } "+" { return '+'; } "-" { return '-'; } "" { return '*'; } "/" { return '/'; } "%" { return '%'; } "^" { return '^'; } "xor" { return '^'; } "&" { return '&'; } "bitand" { return '&'; }

"<<" { return SL; } ">>" { return SR; } "<<=" { return SLEQ; } ">>=" { return SREQ; } "==" { return EQ; } "!=" { return NOTEQ; } "not_eq" { return NOTEQ; } "<=" { return LTEQ; } ">=" { return GTEQ; } "&&" { return ANDAND; } "and" { return ANDAND; } "||" { return OROR; } "or" { return OROR; } "++" { return PLUSPLUS; } "--" { return MINUSMINUS; } "," { return ','; } "->*" { return ARROWSTAR; } "->" { return ARROW; }

"asm" { return ASM; } "auto" { return AUTO; } "bool" { return BOOL; } "break" { return BREAK; } "case" { return CASE; } "catch" { return CATCH; } "char" { return CHAR; } "class" { return CLASS; } "const" { return CONST; } "const_cast" { return CONST_CAST; } "continue" { return CONTINUE; } "default" { return DEFAULT; } "delete" { return DELETE; } "do" { return DO; } "double" { return DOUBLE; } "dynamic_cast" { return DYNAMIC_CAST; } "else" { return ELSE; } "enum" { return ENUM; } "explicit" { return EXPLICIT; } "export" { return EXPORT; }

"short" { return SHORT; } "signed" { return SIGNED; } "sizeof" { return SIZEOF; } "static" { return STATIC; } "static_cast" { return STATIC_CAST; } "struct" { return STRUCT; } "switch" { return SWITCH; } "template" { return TEMPLATE; } "this" { return THIS; } "throw" { return THROW; } "true" { return TRUE; } "try" { return TRY; } "typedef" { return TYPEDEF; } "typeid" { return TYPEID; } "typename" { return TYPENAME; } "union" { return UNION; } "unsigned" { return UNSIGNED; } "using" { return USING; } "virtual" { return VIRTUAL; } "void" { return VOID; }

"volatile" { return VOLATILE; } "wchar_t" { return WCHAR_T; } "while" { return WHILE; } [a-zA-Z_][a-zA-Z_0-9]* { return check_identifier(yytext); } "0"[xX][0-9a-fA-F]+{intsuffix}? { return INTEGER; } "0"[0-7]+{intsuffix}? { return INTEGER; } [0-9]+{intsuffix}? { return INTEGER; }

. { fprintf(stderr, "%d: unexpected character `%c'\n", lineno, yytext[0]); } %% static int yywrap(void) { return 1; }

static void skip_comment(void) { int c1, c2; c1 = input(); c2 = input(); while(c2 != EOF && !(c1 == '*' && c2 == '/')) { if (c1 == '\n') ++lineno; c1 = c2; c2 = input(); } }