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%{
#include <stdio.h>
#define true 1
#define false 0
int lookahead;
int lookahead1;
int error;
int count;
%}
%%
[(] {return(111);}
[)] {return(222);}
[0-9] {return(333);}
[a-zA-Z] {return(444);}
[\+] {return(33);}
[\*] {return(44);}
[\/] {return(55);}
[\-] {return(66);}
[ \n\t] {return(0);}
%%
struct node
{
char a;
struct node * left;
struct node * right;
};
struct node *root, * current;
void insert( struct node ** tree, struct node *item)
{
printf("%c", item -> a);
// printf("%c", &(*tree) -> left);
if (!(*tree))
{
*tree = item;
return;
}
if ( item-> a == '+' || item-> a == '-' || item->a == '*' || item->a == '/' )
{
item -> left = tree;
break;
/* struct node ** temp;
temp= tree;
*tree = item;
(*tree) -> left = *temp;
*/
//insert (&(*tree) -> left, item);
}
else if ( (*tree) -> left == NULL )
{
insert (&(*tree) -> left, item);
}
else
{
insert (&(*tree) -> right, item);
}
}
Goal ()
{
return Expr();
}
Expr()
{
if ( Term() )
return ExprP();
else
return false;
}
ExprP()
{
if ( lookahead == 33 || lookahead == 66 )
{
current = malloc(sizeof(struct node));
current -> a = yytext[0];
current -> left = NULL;
current -> right = NULL;
insert(&root, current);
lookahead = yylex();
if ( Term() )
return ExprP();
else
return false;
}
else if ( lookahead == 222 || lookahead == 0 )
return true;
else
return false;
}
Term()
{
if (Factor())
{
return TermP();
}
else
return false;
}
TermP()
{
if ( lookahead == 44 || lookahead == 55 )
{
current = malloc(sizeof(struct node));
current -> a = yytext[0];
current -> left = NULL;
current -> right = NULL;
insert(&root, current);
lookahead = yylex();
if ( Factor() )
{
return TermP();
}
else
return false;
}
else if ( lookahead == 33 || lookahead == 222 || lookahead == 0 || lookahead == 66 )
return true;
else
return false;
}
Factor()
{
if (lookahead == 111 )
{
lookahead = yylex();
if ( !Expr() )
return false;
if ( lookahead != 222 )
return false;
lookahead = yylex();
return true;
}
else if ( lookahead == 333 )
{
current = malloc(sizeof(struct node));
current -> a = yytext[0];
current -> left = NULL;
current -> right = NULL;
insert(&root, current);
lookahead = yylex();
return true;
}
else
return false;
}
int yywrap(void)
{
return 1;
}
void printout(struct node * tree, int h) {
if(tree->right) printout(tree->right, h+1);
int i ;
for ( i = 0; i < h ; i++)
printf(" ");
printf("%c\n",tree->a);
if(tree->left) printout(tree->left, h+1);
}
int main()
{
root = NULL;
lookahead = yylex();
if ( Goal() )
printf ("\n\nThe string you entered successfully accepted\n\n");
else
{
printf("\n\nThe string you entered failed to accept\n\n");
printf("%s\n", yytext);
}
printout(root, 0);
return 0;
}
|
