Added stack files, with push().

lib/stack.c

@@ -0,0 +1,45 @@
+#include <malloc.h>
+#include <stdbool.h>
+#include "card.h"
+#include "stack.h"
+
+struct stack *initialize_stack() {
+  struct stack *stack = NULL;
+
+  stack = malloc(sizeof(stack));
+
+  stack->card  = NULL;
+  stack->next = NULL;
+
+  return(stack);
+}
+
+bool empty(struct stack *stack) {
+  return(stack->card == NULL);
+}
+
+int length(struct stack *stack) {
+  int length = 0;
+
+  if (!empty(stack)) {
+    length = 1;
+    while (stack->next != NULL) {
+      length++;
+    }
+  }
+
+  return(length);
+}
+
+void push(struct stack *stack, struct card *card) {
+  struct stack *new_stack = NULL;
+
+  if (empty(stack)) {
+    stack->card = card;
+  } else {
+    new_stack = malloc(sizeof(new_stack));
+    new_stack->card = card;
+    new_stack->next = stack;
+    stack = new_stack;
+  }
+}

lib/stack.h

@@ -0,0 +1,9 @@
+#ifndef STACK_H
+#define STACK_H
+
+struct stack {
+  struct card  *card;
+  struct stack *next;
+};
+
+#endif