rename function peek into stack_peek

stack.c

 #include <stdio.h>
 #include "stack.h"
 
-void peek(stack s, int *value){
+void stack_peek(stack s, int *value){
     if(s.top>-1 && s.top<s.capacity){
         *value=s.data[s.top];
     }

stack.h

@@ -7,6 +7,6 @@ typedef struct _stack {
     int top;
 } stack;
 
-void peek(stack s, int *value);
+void stack_peek(stack s, int *value);
 
 #endif