I found some code to make a C implementation of stacks, and decided to use it. However, there were several typedefs, and I am having difficulty printing the values in a stackT (really a char array). Below is the code. What am I doing wrong?
#include <stdio.h>
#include <stdlib.h>
typedef char stackElementT;
typedef struct {
stackElementT *contents;
int maxSize;
int top;
} stackT;
void StackInit(stackT *stackP, int maxSize) {
stackElementT *newContents;
newContents = (stackElementT *)malloc(sizeof(stackElementT)*maxSize);
if (newContents == NULL) {
fprintf(stderr, "Not enough memory.\n");
exit(1);
}
stackP->contents = newContents;
stackP->maxSize = maxSize;
stackP->top = -1; //empty...
}
void StackDestroy(stackT *stackP) {
free(stackP->contents);
stackP->contents = NULL;
stackP->maxSize = 0;
stackP->top = -1; //empty
}
int StackIsEmpty(stackT *stackP) {
return stackP->top < 0;
}
int StackIsFull(stackT *stackP) {
return stackP->top >= stackP->maxSize-1;
}
void StackPush(stackT *stackP, stackElementT element) {
if(StackIsFull(stackP)) {
fprintf(stderr, "Can't push element: stack is full.\n");
exit(1);
}
stackP->contents[++stackP->top] = element;
}
stackElementT StackPop(stackT *stackP) {
if(StackIsEmpty(stackP)) {
fprintf(stderr, "Can't pop element: stack is empty.\n");
exit(1);
}
return stackP->contents[stackP->top--];
}
void StackDisplay(stackT *stackP) {
if(StackIsEmpty(stackP)) {
fprintf(stderr, "Can't display: stack is empty.\n");
exit(1);
}
int i;
printf("[ ");
for (i = 0; i < stackP->top; i++) {
printf("%c, ", stackP[i]);
}
printf("%c ]", stackP[stackP->top]);
}
int postfix(char* expr, int length) {
int i;
stackT stack;
StackInit(&stack, 1000);
int temp;
for (i = 0; i < length; i++) {
if ((expr[i] >= 48) && (expr[i] <= 57)) {
printf("Is a number! Pushed %d\n", expr[i]);
StackPush(&stack, expr[i]);
}
else {
switch (expr[i]) {
case 43: {
temp = StackPop(&stack);
StackPush(&stack, StackPop(&stack)+temp);
}
break;
case 45: {
temp = StackPop(&stack);
StackPush(&stack, StackPop(&stack)-temp);
}
break;
case 47: {
temp = StackPop(&stack);
StackPush(&stack, StackPop(&stack)/temp);
}
break;
case 42: {
temp = StackPop(&stack);
StackPush(&stack, StackPop(&stack)*temp);
}
break;
default:
break;
}
}
}
return StackPop(&stack);
}
int main() {
int i;
char* expr = "1 2 3 + * 3 2 1 - + *";
for(i = 0; expr[i] != '\0'; i++) ;
printf("%d\n", postfix(expr, i));
}
