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POC Typed Stack: Linked-List Implementation
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copied!<p>I have a computer science exam coming up and a large portion is going to be on programming in ansi C. I'm new to C and as a review I tried to implement a stack using a linked-list. My code compiles but it doesn't run as expected.</p> <p>I believe there is an error with my push() function. I'm assuming that my stack reference isn't being updated properly.</p> <p>I wrote the following code from scratch to study / practice. Any advice on how to fix my code or improve my programming style would be greatly appreciated.</p> <p>Thanks guys!</p> <hr> <p><strong>stack.h</strong></p> <pre><code>#ifndef __STACK__ #define __STACK__ #include <stdlib.h> #include "bool.h" #define EMPTY -1 typedef struct Node { int index; enum { INT = 0, CHAR, STRING } type; union { int i; char c; char* s; } value; struct Node* prev; } Node; typedef Node* Stack; Stack init(); void push(Stack stack, int type, void* value); void pop(Stack stack, Node* node); void empty(Stack stack); Bool isempty(Stack stack); #endif </code></pre> <p><strong>stack.c</strong></p> <pre><code>#include <stdlib.h> #include <string.h> #include "stack.h" Stack init() { Stack stack = (Node*) malloc(sizeof(Node)); stack->index = EMPTY; stack->type = INT; stack->value.i = 0; stack->prev = 0; return stack; } void push(Stack stack, int type, void* value) { int length; Node* node = (Node*) malloc(sizeof(Node)); node->index = stack->index + 1; node->type = type; switch(node->type) { case INT: node->value.i = *((int*) value); break; case CHAR: node->value.c = *((char*) value); break; case STRING: length = strlen((char*) value) + 1; node->value.s = (char*) malloc(length * sizeof(char)); strcpy(node->value.s, value); break; } node->prev = stack; stack = node; } void pop(Stack stack, Node* node) { int length; Node* temp = stack; if (!isempty(stack)) { node->index = stack->index; node->type = stack->type; switch(stack->type) { case INT: node->value.i = stack->value.i; break; case CHAR: node->value.c = stack->value.c; break; case STRING: length = strlen(stack->value.s) + 1; node->value.s = (char*) malloc(length * sizeof(char)); strcpy(node->value.s, stack->value.s); free(stack->value.s); break; } node->prev = 0; stack = stack->prev; free(temp); } else { /*TODO: handle empty case */ puts("Stack empty!"); } } void empty(Stack stack) { while (!isempty(stack)) { Node* temp = malloc(sizeof(Node)); pop(stack, temp); free(temp); } } Bool isempty(Stack stack) { return stack->index == EMPTY ? TRUE : FALSE; } </code></pre> <p><strong>bool.h</strong></p> <pre><code>#ifndef __BOOL__ #define __BOOL__ typedef int Bool; #define FALSE 0 #define TRUE 1 #endif </code></pre> <p><strong>main.c</strong></p> <pre><code>#include <stdlib.h> #include <stdio.h> #include "stack.h" int main() { Stack stack = init(); Node* node = malloc(sizeof(Node)); int i = 5; push(stack, 0, &i); pop(stack, node); printf("Node value: %d\n", node->value.i); free(node); empty(stack); puts("done."); return 0; } </code></pre>

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