Re: Another bison problem

[Andrei Harangus]

Thanks,

Actually I was trying to analize a C-like language, and indeed I kind of
messed up the grammar. But, with a little help, I solved it eventually.

Kind regards, Andrei


>From: Hans Aberg <address@hidden>
>To: "Andrei Harangus" <address@hidden>
>CC: Help Bison <address@hidden>
>Subject: Re: Another bison problem
>Date: Wed, 2 Apr 2003 19:08:58 +0200
>
>At 15:57 +0300 2003/04/02, Andrei Harangus wrote:
> >    Hy,   After solving the previous problem I would  like to direct your
> >attention to a more complicated one. I am writing a rather large grammar
> >that  generates shift/reduce and reduce/reduce conflicts: ... call : ID
> >'(' call_list ')'  {;} call_list : expr ',' call_list           | call
> >',' call_list           |  expr           |  call ;   expr : ...      |
> >call <-- HERE  IT DOES ; ...   I know that the grammar is ambiguous,  but
> >I was wondering wether just by defining operator priorities I could solve
> >the problem (which I wasn't  able to do), or I'll have to change the
> >grammar (and I don't know how).
>
>You are mixing together "call" and "expr" without thinking about their
>exact relation, it seems. It looks to me as though your "call" is something
>like the definition of a "structure" in a Prolog grammar, so I attach such
>a grammar I once made. It has some extensions typical for expressions using
>precedence rules, you might be able to copy over and change relevant parts.
>Just start at
>   structure:
>     ...
>     | atom term_sequence
>     ...
>and trace the rules to extract the parts that might be relevant to you.
>
>
>%token help_key
>%token quit_key
>%token show_substitutions_key, no_show_substitutions_key
>%token debug_key "debug"
>
>%token show_key "??"
>
>%token Prolog_key "Prolog"
>%token query_key "?-"
>%token query_pure_key "?+"
>%token query_Andorra_key "?*"
>
>%token if_key ":-"
>%token cut_key "!"
>
>%token variable_name "variable name"
>%token atom_name "atom name"
>%token integer_value
>%token list_concat "++"
>
>%token solve_key "solve"
>%token axiom_key "axiom"
>%token definition_key "definition"
>%token theorem_key "theorem"
>%token proof_key "proof"
>
>%token identifier_key "identifier"
>
>%token all_key "all"
>%token implies_key "=>"
>%token impliedby_key "<="
>%token in_key "in"
>
>
>%nonassoc '='
>%nonassoc "in"
>
>%left '+' '-'
>%right UMINUS
>%left "++"
>
>%%
>file:
>     file_contents { }
>   |               { }
>   | error {
>       clp_parser_context = 0;
>       YYABORT;
>     }
>
>file_contents:
>     file_contents command { }
>   | command               { }
>
>command:
>     help_key { clp::help(std::cout); }
>   | quit_key { std::cout << "Thank you and goodbye." << std::endl;
>std::exit(EXIT_SUCCESS); }
>   | show_substitutions_key { clp::show_substitutions = true; }
>   | no_show_substitutions_key { clp::show_substitutions = false; }
>   | show_key { db->show(std::cout); }
>   | debug_key '-' { clp::debug_unification = false; }
>   | debug_key '+' { clp::debug_unification = true; }
>   | "Prolog" Prolog_clause { clp_parser_context = 0;
>db->addClause($2.clause); }
>   | "Prolog" '{' Prolog_clauses '}' { clp_parser_context = 0; }
>   | Prolog_query { clp_parser_context = 0; }
>   | "solve" query { }
>   | "axiom" clause { clp_parser_variables.clear();
>db->addClause($2.clause); }
>
>Prolog_clauses:
>     Prolog_clause { db->addClause($1.clause); }
>   | Prolog_clauses Prolog_clause { db->addClause($2.clause); }
>
>Prolog_clause:
>     structure '.' { $$.clause = $1.term; }
>   | structure Prolog_if_clause '.' { $$.clause = clp::Clause($1.term,
>$2.termlist); }
>
>clause:
>     structure '.' { $$.clause = $1.term; }
>   | variables_declaration structure '.' {
>       if ($1.termlist.empty())
>         $$.clause = $2.term;
>       $$.clause = clp::Clause($2.term, $1.termlist);
>     }
>   | variables_declaration structure "<=" termlist '.' {
>       $4.termlist.insert($4.termlist.begin(), $1.termlist.begin(),
>$1.termlist.end());
>       $$.clause = clp::Clause($2.term, $4.termlist); }
>   | variables_declaration termlist "=>" structure '.' {
>       $2.termlist.insert($2.termlist.begin(), $1.termlist.begin(),
>$1.termlist.end());
>       $$.clause = clp::Clause($4.term, $2.termlist); }
>
>variables_declaration:
>     "all" { clp_parser_variables.clear(); } identifier_list in_set ':' {
>       $$.termlist = $4.termlist;
>     }
>
>in_set:
>       { }
>   | "in" atom {
>       std::set<std::string>::iterator i = clp_parser_variables.begin(), i1
>= clp_parser_variables.end();
>       for (; i != i1; ++i) {
>         $1.termlist.push_back(new clp::variable(0, *i));
>         $$.termlist.push_back(
>           new clp::Structure($2.text, $1.termlist));
>         $1.termlist.clear();
>       }
>     }
>
>identifier_list:
>     atom_name { clp_parser_variables.insert($1.text); }
>   | identifier_list ',' atom_name { clp_parser_variables.insert($3.text);
>}
>
>structure:
>     atom { $$.term = new clp::Structure($1.text); }
>   | atom term_sequence { $$.term = new clp::Structure($1.text,
>$2.termlist); }
>   | term "in" atom {
>       $1.termlist.push_back($1.term);
>       $$.term = new clp::Structure($3.text, $1.termlist);
>     }
>   | term '=' term {
>       $1.termlist.push_back($1.term);
>       $1.termlist.push_back($3.term);
>       $$.term = new clp::Structure("=", $1.termlist);
>     }
>
>atom:
>     atom_name { $$.text = $1.text; }
>
>Prolog_if_clause:
>     ":-" termlist { $$.termlist = $2.termlist; }
>
>term_sequence:
>     '(' termlist ')' { $$.termlist = $2.termlist; }
>
>termlist:
>     term              { $$.termlist.push_back($1.term); }
>   | termlist ',' term { $$.termlist = $1.termlist;
>$$.termlist.push_back($3.term); }
>
>term:
>     variable_name { $$.term = new clp::variable(0, $1.text); }
>   | integer_value { $$.term = new clp::integer($1.number); }
>   | structure { $$.term = $1.term; }
>   | list { $$.term = $1.term; }
>   | term "++" term { $$.term = new clp::list_concatenation($1.term,
>$3.term); }
>   | term '+' term { $$.term = new clp::integer_addition($1.term, $3.term);
>}
>   | term '-' term { $$.term = new clp::integer_addition($1.term,
>     new clp::integer_negative($3.term)); }
>   | '-' term  %prec UMINUS { $$.term = new clp::integer_negative($2.term);
>}
>
>list:
>     '[' termlist ']' { $$.term = new clp::list($2.termlist); }
>   | '[' ']' { $$.term = new clp::list(); }
>   | '[' termlist '|' term ']' { $$.term = new
>clp::list_constructor($2.termlist, $4.term); }
>
>Prolog_query:
>     "?-" termlist '.' { db->demonstrate($2.termlist); }
>   | "?+" termlist '.' { db->demonstrate($2.termlist, clp::Database::pure);
>}
>   | "?*" termlist '.' { db->demonstrate($2.termlist,
>clp::Database::Andorra); }
>
>query:
>     termlist '.' { db->demonstrate($1.termlist); }
>   | variables_declaration termlist '.' {
>       $2.termlist.insert($2.termlist.begin(), $1.termlist.begin(),
>$1.termlist.end());
>       clp_parser_variables.clear();
>       db->demonstrate($2.termlist);
>     }
>
>%%
>
>

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