evaluate postfix expressions read from infile
hello im pretty sure im on the right track but i get errors in my code that cannot convert strings op1 and op2 and such can anyone help?
Code:
# include <stdio.h>
# include <stdlib.h>
# include <ctype.h>
# include <string.h>
#define TRUE 1
#define FALSE 0
struct info_node
{
int weight ;
struct info_node* next ;
} ;
struct nstack
{
struct info_node* top ;
} ;
void create_stack(struct nstack*) ;
int empty_stack(struct nstack*) ;
void push_stack(struct nstack* , struct info_node*) ;
struct info_node* pop_stack( struct nstack* ) ;
int calc(int, int, int) ;
int main()
{
FILE* infile ;
int a = 0 ;
int num = 0 ;
char input_line[31] ;
struct nstack even_Stack ;
struct info_node* pnew_node = NULL ;
struct info_node* ppop_node = NULL ;
create_stack(&even_Stack) ;
infile = fopen("express.txt", "r") ;
while (!feof(infile) )
{
fgets(input_line, 31, infile) ;
// printf("%s \n", input_line) ;
a = 0 ;
while(input_line[a] != '\0')
{
if( isspace(input_line[a]))
printf(" SPACE ") ;
else if( isdigit(input_line[a] ))
{
num = atoi(&input_line[a]) ; //converts from character to integer
push_stack(&even_Stack, num) ;
//push to stack
printf("%d ", num ) ;
}
else
int result = 0 ;
//must be operater pop twice and push to stack
printf("%c", input_line[a]) ;
num = input_line[a] ;
int op1;
int op2;
op1 = pop_stack(&even_Stack) ;
op2 = pop_stack(&even_Stack) ;
calc(&op1, &num, &op2) ;
push_stack(&even_Stack, result) ;
result = pop_stack(&even_Stack);
printf("%d ", result) ;
a++;
}
printf("\n") ;
}
fclose(infile) ;
return (0) ;
} //end of function main
int calc(int op1, int oper, int op2)
{
int result = 0 ;
switch(oper)
{
case '+' : result = op1 + op2 ;
break;
case '-' : result = op1 - op2 ;
break;
case '*' : result = op1 * op2 ;
break;
case '/' : result = op1 / op2 ;
break;
}
return(result) ;
} //end of func calc()
void create_stack(struct nstack* pnstack)
{
pnstack->top = NULL ;
return ;
} //end of func create_stack
int empty_stack(struct nstack* pnstack)
{
if (pnstack->top == NULL)
return (TRUE) ;
else
return (FALSE) ;
} //end of func empty_stack
void push_stack(struct nstack* pnstack, struct info_node* pnnode)
{
if(empty_stack(pnstack))
{
pnstack->top = pnnode ;
pnnode->next = NULL ;
}
else
{
pnnode->next = pnstack->top ;
pnstack->top = pnnode ;
}
return ;
} //end of func push_stack
struct info_node* pop_stack( struct nstack* pnstack )
{
struct info_node* prnode = NULL ;
if(empty_stack(pnstack) )
printf("ERROR: STACK IS EMPTY!!! \n") ;
else
{
prnode = pnstack->top ;
pnstack->top = pnstack->top->next ;
prnode->next = NULL ;
}
return( prnode ) ;
} // end of func pop_stack
also here is the numbers from the infile:
1 2 3 * 4 / +
1 2 3 4 / * +
1 2 + 3 * 4 /
1 2 + 4 3 / *
1 2 3 * + 4 /
4 3 / 1 2 + *
6 7 8 / 9 * -
6 7 8 9 * / -
6 7 - 8 / 9 *
6 7 - 9 8 * /
6 7 8 / - 9 *
8 9 * 6 7 - /
