From fa90ad17dbe0cbdea10bd4b020e48f94d56b3807 Mon Sep 17 00:00:00 2001
From: Jon Lewis <jon.lewis@xenami.net>
Date: Tue, 16 Oct 2018 20:58:34 -0500
Subject: [PATCH] Converted push/pop to pass by ref

---
 ee.c | 65 +++++++++++++++++++++++++++++++++++++-----------------------
 ee.h |  8 ++++----
 2 files changed, 44 insertions(+), 29 deletions(-)

diff --git a/ee.c b/ee.c
index cdce3e5..3f9c714 100644
--- a/ee.c
+++ b/ee.c
@@ -1,34 +1,37 @@
 #include "ee.h"
 int error = 0;
-
+void printStack(STACK);
 int
-main (int argc, const char* argv[]){
+main (const int argc, const char* argv[]){
     
     STACK expr = NULL;
+
     const char** endPtr = argv+argc,
               ** arg    = argv+1   ;
     
     while ((arg < endPtr) && (!error)){
                
         if (arrity(**arg))
-           expr = push(evaluate(&expr, **arg), expr);
-        
+            push(evaluate(&expr, **arg), &expr);
+           
         else if(isNum(*arg))
-           expr = push(strtod(*arg,NULL), expr);
+            push(strtod(*arg,NULL), &expr);
         
         else
             error |= ERR_INVALID_INPUT;
         
-        arg++;
+
+        arg += 1;
+
     }
     
     if (expr == NULL)
         error |= ERR_NS_OPERANDS;
         
-    else if (expr->tail!=NULL)
+    else if ((*expr).tail != NULL)
         error |= ERR_NS_OPERATORS;
-    
-    report(expr);
+
+    report(&expr);
         
     return error;
 }
@@ -131,8 +134,8 @@ operands(STACK* target_stack, int size){
     double * endPtr = _operands + size;
     while ((tPtr < endPtr) && !error)
     {
-        *tPtr = peek((*target_stack));
-        (*target_stack) = pop(*target_stack);
+        *tPtr = peek((target_stack));
+        pop(target_stack);
         
         tPtr += 1;
     }
@@ -148,13 +151,14 @@ fact(int n){
 }
 
 void 
-report(STACK expr){
+report(STACK* expr){
     /*
      * reportErrors() prints error strings according to the value of global
      * bitvector error if it is nonzero, or the result of evaluation if error
      * is zero.
      */
      
+    //printStack(expr);
     if (error & ERR_INVALID_INPUT)
         printf("Error: Unexpected input.\n");
         
@@ -171,38 +175,49 @@ report(STACK expr){
         printf("%g\n", peek(expr));
 }
 
-STACK
-push(double datum, STACK tail){
+void
+printStack(STACK s){
+    /* Given a stack, print "datum  tail"*/
+    
+    while (s != NULL){
+        printf("%g\t%p\n", s->datum, s->tail);
+        s = s->tail;
+    }   
+    printf("%s\n", "-----");
+}
+
+void
+push(double datum, STACK* tail){
     /* Given a double value (datum), and a STACK (tail),
      * push(datum,tail) is the STACK resulting from
      * prepending datum to the STACK tail.
      */
      NODE* new_node = (NODE*)malloc(sizeof(NODE));
         (*new_node).datum = datum;
-        (*new_node).tail  = tail;
-    return new_node;
+        (*new_node).tail  = *tail;
+    (*tail) = new_node;
 }
 
-STACK
-pop(STACK target_stack){
+void
+pop(STACK* target_stack){
     /* Given a STACK (target_stack), pop(target_stack)
      * is the STACK resulting from the removal of the first
      * item in target_stack;
      */
-     
+
      STACK tail = NULL;
      
-     if (target_stack != NULL){ 
-        tail = (*target_stack).tail;
-        free(target_stack);
+     if ((*target_stack) != NULL){ 
+        tail = (*target_stack)->tail;
+        free(*target_stack);
      }
-     return tail;
+     (*target_stack) = tail;
 }
 
 double
-peek(STACK target_stack){
+peek(STACK* target_stack){
     /* Given a STACK (target_stack), peek(STACK)
      * is the first element's datum.
      */
-     return (target_stack)? (*target_stack).datum : 0;
+     return (*target_stack)? (*target_stack)->datum : 0;
 }
diff --git a/ee.h b/ee.h
index 1fff3c1..c94f4de 100644
--- a/ee.h
+++ b/ee.h
@@ -18,9 +18,9 @@ struct EE_STACK_NODE {
 typedef struct EE_STACK_NODE NODE;
 typedef struct EE_STACK_NODE* STACK;
 
-STACK   push(double,STACK);
-STACK   pop(STACK);
-double  peek(STACK);
+void   push(double,STACK*);
+void   pop(STACK*);
+double  peek(STACK*);
 
 int     isNum(const char*);
 int     arrity(const char);
@@ -29,7 +29,7 @@ double  evaluate(STACK*, char);
 double* operands(STACK*, int);
 double  fact(int n);
 
-void    report();
+void    report(STACK*);