i've been working on this program forever! now i'm stuck and going
insane because i keep getting a syntax error msg and i just can't see
what the compiler is signaling to!
the error msg i get is: syntax error before "switch"
i don't get it :S ... any suggestions?
insane because i keep getting a syntax error msg and i just can't see
what the compiler is signaling to!
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
/* constants */
#define TRUE 1
#define FALSE 0
/* structure for stack */
typedef struct
{
char data[40]; /* array to hold stack contents */
int tos; /* top of the stack pointer */
}
STACK;
/* function prototypes */
void initStack(STACK *stack);
void get_infix(char infix[]);
void convertToPostfix(char infix[], char postfix[]);
int isOperator(char c);
int precedence(char operator1, char operator2);
int pred_level(char ch);
void push(STACK *stack, char value);
char pop(STACK *stack);
char stackTop(STACK *stack);
int isEmpty(STACK *stack);
int isFull(STACK *stack);
void printResult(char infix[], char postfix[]);
void print_msg(void);
/* program entry point */
int main()
{
char infix[40], postfix[40]="";
/* convert from infix to postfix main function */
convertToPostfix(infix, postfix);
/* display the postfix equivalent */
infix[strlen(infix)-2] = '\0';
printResult(infix, postfix);
return EXIT_SUCCESS;
}
/* initalise the stack */
void initStack(STACK *stack)
{
stack->tos = -1; /* stack is initially empty */
}
/* get infix expression from user */
void get_infix(char infix[])
{
int i;
printf("Enter infix expression: ");
fflush(stdin);
for ( i=0; i<40; )
{
if ( (infix[i] = getchar()) == '\n' )
{
i++;
break;
}
else if ( !(isspace(infix[i])) )
i++;
}
infix[i] = '\0';
}
/* convert the infix expression to postfix notation */
void convertToPostfix(char infix[], char postfix[])
{
int i, length;
int j=0;
char tos_ch;
STACK stack;
initStack(&stack); /* initialise stack */
get_infix(infix); /* get infix expression from user */
length = strlen(infix);
if ( length )
{
push(&stack, '(');
strcat(infix, ")");
length++;
for ( i=0; i<length; i++ )
{
/* if current operator in infix is digit */
if ( isdigit(infix[i]) )
{
postfix[j++] = infix[i];
}
/* if current operator in infix is left parenthesis */
else if ( infix[i] == '(' )
{
push(&stack, '(');
}
/* if current operator in infix is operator */
else if ( isOperator(infix[i]) )
{
while ( TRUE )
{
/* get tos */
tos_ch = stackTop(&stack);
/* no stack left */
if ( tos_ch == '\0' )
{
printf("\nFull Stack!\n");
print_msg();
exit(1);
}
else
{
if ( isOperator(tos_ch) )
{
if ( pred_level(tos_ch) >=
pred_level(infix[i]) )
postfix[j++] = pop(&stack);
else
break;
}
else
break;
}
}
push(&stack, infix[i]);
}
/* if current operator in infix is right parenthesis */
else if ( infix[i] == ')' )
{
while ( TRUE )
{
/* get tos */
tos_ch = stackTop(&stack);
/* no stack left */
if ( tos_ch == '\0' )
{
printf("\nFull Stack!\n");
print_msg();
exit(1);
}
else
{
if ( tos_ch != '(' )
{
postfix[j++] = tos_ch;
pop(&stack);
}
else
{
pop(&stack);
break;
}
}
}
continue;
}
}
}
postfix[j] = '\0';
}
/* determine if c is an operator */
switch (c) {
case '+':
return TRUE;
break;
case '-':
return TRUE;
break;
case '*':
return TRUE;
break;
case '/':
return TRUE;
break;
default:
return FALSE;
break;
/*if ( c == '+' || c == '-' || c == '*' ||
c == '/' || c == '%' || c == '^' )
{
return TRUE;
}
else
return FALSE; */
}
/* determine precedence level */
int pred_level(char ch)
{
if ( ch == '+' || ch == '-' )
return 1;
else
return 2;
}
/* determine if the precedence of operator1 is less than,
equal to, greater than the precedence of operator2 */
int precedence(char operator1, char operator2)
{
if ( pred_level(operator1) > pred_level(operator2) )
return 1;
else if ( pred_level(operator1) < pred_level(operator2) )
return -1;
else
return 0;
}
/* push a value on the stack */
void push(STACK *stack, char value)
{
if ( !(isFull(stack)) )
{
(stack->tos)++;
stack->data[stack->tos] = value;
}
}
/* pop a value off the stack */
char pop(STACK *stack)
{
char ch;
if ( !(isEmpty(stack)) )
{
ch = stack->data[stack->tos];
(stack->tos)--;
return ch;
}
else
return '\0';
}
/* return the top value of the stack without popping the stack */
char stackTop(STACK *stack)
{
if ( !(isEmpty(stack)) )
return stack->data[stack->tos];
else
return '\0';
}
/* determine if stack is empty */
int isEmpty(STACK *stack)
{
/* empty */
if ( stack->tos == -1 )
return TRUE;
/* not empty */
else
return FALSE;
}
/* determine if stack is full */
int isFull(STACK *stack)
{
/* full */
if ( stack->tos == 19 )
return TRUE;
/* not full */
else
return FALSE;
}
/* display the result postfix expression */
void printResult(char infix[], char postfix[])
{
/*system("cls");*/
printf("\n\n");
printf("Infix notation: %d%s\n", infix);
printf("Postfix notation: %d%s\n\n", postfix);
print_msg();
}
/* print exit message */
void print_msg(void)
{
printf("Hit <RETURN> to exit...");
fflush(stdin);
getchar();
}
i don't get it :S ... any suggestions?
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