[munday63]

Hi,

I have the following yacc code, and need to print out the parse tree created using the newnode. I need to print the tree using a printtree function.

Can anyone help me to create the printtree function?

This is my lex code:

%%
[01]            return(CONST);
[a-z]           return(VARIA);
"<=>"           return(EQUIV);
"=>"            return(IMPLY);
"|"             return(OR);
"&"             return(AND);
"~"             return(NOT);
[PRE]           return(KEY);
[C][1-7]        return(LEVEL);
[ \t\n]                 ;
"("             return(LBRAC);
")"             return(RBRAC);
";"             return(END);
"{"             return(LCURL);
"}"             return(RCURL);
.               printf( "Unexpected: %s\n", yytext);
%%

This is my yacc code:

typedef struct node *noderef;

union nodeorval {
        noderef nodeval;
        int intval;
        char *strval;
        };

struct node {
        char nodetype;
        union nodeorval leftarg, rightarg;
        };

#define NIL     (noderef) 0

noderef newnode(char sym, noderef l, noderef r)
        {
        noderef new;
        new = (noderef) malloc (sizeof (struct node));
        new -> nodetype = sym;
        new -> leftarg.nodeval = l;
        new -> rightarg.nodeval = r;
        return new;
        };

%start task

%union {
        int tokenval;
        noderef nodeval;
        }

%token  LEVEL KEY CONST VARIA LCURL RCURL END LBRAC RBRAC
%left EQUIV
%right IMPLY
%left AND OR
%nonassoc NOT

%type <nodeval> wff expr

%%
task    :       taskid LCURL wfflist RCURL
        |       error           {printf("TASK-P>Error\n");}
        ;
taskid  :       LEVEL
        |       KEY
        |       error           {printf("TASK-P>Error\n");}
        ;
wfflist :       wff wfflist
        |       wff
        ;
wff     :       expr END        {printf("TASK-P>Success\n");
                                        printtree($1);}
        |       error END       {printf("TASK-P>Error\n");}
        ;
expr    :       CONST
                        {$$ = newnode(yytext[0],NIL,NIL);}
        |       VARIA
                        {$$ = newnode(yytext[0],NIL,NIL);}
        |       expr EQUIV expr
                        {$$ = newnode('E',$1,$3);}
        |       expr IMPLY expr
                        {$$ = newnode('I',$1,$3);}
        |       expr OR expr
                        {$$ = newnode('|',$1,$3);}
        |       expr AND expr
                        {$$ = newnode('&',$1,$3);}
        |       NOT expr
                        {$$ = newnode('~',NIL,$2);}
        |       LBRAC expr RBRAC
                        {$$ = $2;}
        ;
%%

/*void yyerror(char *err){
        fprintf(stderr, "%s\n", err);
        }

int main(void){
        return yyparse();
}*/

#include "lex.yy.c"