yacc

Thinking about parsing regular expressions using yacc (I'm actually using PLY), some of the rules would be like the following: expr : expr expr expr : expr '|' expr expr : expr '*' The problem is, the first rule(concatenation) must take precedence over the second rule, but not the third one. However, the concatenation rule has no operator in it. How can I specify the precedence correctly in this case? Thank you! EDIT: I modified the rules to avoid the issue, but I'm still curious what was the problem. Here is the source code: tokens = ['PLEFT', 'PRIGHT', 'BAR', 'ASTERISK', 'NORMAL'] t_PLEFT =

I know how to make YACC generate an AST, but how do you actaully get it? I mean, how do you actaully get the value of the root node from YACC? Yacc only gives you back one node at a time, and it's always something that you just gave yacc at some earlier time, i.e., whatever you wanted to return from a reduced production or whatever you wanted to return from a terminal symbol. (Sorry, you said you knew that, but some people reading this might not.) So, take whatever you woud have returned from the root or top rule, and save it (in your attached C reduction code) any way you like. What Yacc

In bison, it is sufficient to add %verbose-error to the file to make the parser errors more verbose. Is there any way to gain similar functionality with ocamlyacc? Here is the answer for a similar question, but I could not make anything out of it. This is how I call the lexer and parser functions: let rec foo () = try let line = input_line stdin in (try let _ = (Parser.latexstatement lexer_token_safe (Lexing.from_string line)) in print_string ("SUCCESS\n") with LexerException s -> print_string ("$L" ^ line ^ "\n") | Parsing.Parse_error -> print_string ("$P" ^ line ^ "\n") | _ -> print_string (

With Bison, I figured out how to get everything into one long string as follows: arg_list: WORD arg_list { strcat( $1, "IFS" ); $$ = strcat($1, $2); } | WORD ; and: WORD arg_list { printf("%s, %s\n", $1, $2); } But the problem is that I will then have to split up $2 in the second rule again to parse it. Is there a way to populate an array instead of just using concatenation? Am I going about this the wrong way? If I need to build something like a linked list that could make sense, just not sure what would be the proper way to bind to arg_list, and then clean up the memory. If you have an array

I'm trying to generate a compiler so I can pass him a .c file after. I've downloaded both YACC and LEX grammars from http://www.quut.com/c/ANSI-C-grammar-y.html and named them clexyacc.l and clexyacc.y When generating it on terminal I did : yacc -d clexyacc.y lex clexyacc.l All went fine. When I move on to the last part I get a few errors. The last part is : cc lex.yy.c y.tab.c -oclexyacc.exe But I get these errors : y.tab.c:2261:16: warning: implicit declaration of function 'yylex' is invalid in C99 [-Wimplicit-function-declaration] yychar = YYLEX; ^ y.tab.c:1617:16: note: expanded from macro

How much time would it take to write a C++ compiler using lex/yacc? Where can I get started with it? There are many parsing rules that cannot be parsed by a bison/yacc parser (for example, distinguishing between a declaration and a function call in some circumstances). Additionally sometimes the interpretation of tokens requires input from the parser, particularly in C++0x. The handling of the character sequence >> for example is crucially dependent on parsing context. Those two tools are very poor choices for parsing C++ and you would have to put in a lot of special cases that escaped the