simplify code

Author: fsaadatmand

chapter04/4-11.c

@@ -1,6 +1,7 @@
 /*
  * Exercise 4-11. Modify getop so that it doesn't need to use ungetch. Hint:
  * use an internal static variable.
+ *
  * Faisal Saadatmand
  */
 
@@ -16,7 +17,6 @@
 #define MAXVAL   100          /* maximum depth of val stack */
 #define BUFSIZE  100
 #define MAXVAR   26
-#define TOP      val[sp - 1]  /* top element in stack */
 
 /* functions */
 int    getop(char []);
@@ -36,9 +36,8 @@ void   clearMemory(void);
 int    sp;                   /* next free stack position */
 double val[MAXVAL];          /* value stack */
 double mem[MAXVAR];          /* variables values */
-char   buf[BUFSIZE];         /* buffer from ungetch */
+int    buf[BUFSIZE];         /* buffer from ungetch */
 int    bufp;                 /* next free position in buf */
-int    peak;                 /* flag: peak at top of the stack */
 int    variable;             /* current input variable */ 
 double printed;              /* last printed value */
 
@@ -116,18 +115,18 @@ int getch(void)
 /* printTOP: print top of the stack without pop */
 void printTOP(void)
 {
-	if (sp < 1)
-		printf("stack empty\n");
-	printf("\t%.8g\n", TOP);
+	double top;
+
+	top = pop();
+	printf("\t%.8g\n", top);
+	push(top);
 }
 
 /* duplicateTop: duplicate the top element in the stack */
 void duplicateTop(void)
 {
 	double top;
 
-	if (sp < 1)
-		return;
 	push(top = pop());
 	push(top);
 }
@@ -137,11 +136,6 @@ void duplicateTop(void)
  {
 	 double top1, top2;
 
-	 if (sp < 2) {
-		 if (sp == 1)
-			 printf("error: 1 element in stack\n");
-		 return;
-	 }
 	 top1 = pop();
 	 top2 = pop();
 	 push(top1);
@@ -151,8 +145,7 @@ void duplicateTop(void)
 /* clear: clears the entire stack */
 void clearStack(void)
 {
-	while (sp > 1)
-		pop();
+	sp = 0;
 }
 
 /* mathfunction: call the appropriate math function according to value of s,
@@ -181,7 +174,6 @@ int mathfunction(char s[])
  * location in mem and push back to top of stack */
 void storeVariable(void)
 {
-//	if (isalpha(variable) && islower(variable)) {
 	if (variable >= 'a' && variable <= 'z') {
 		pop();
 		push(mem[variable - 'a'] = pop());
@@ -222,7 +214,6 @@ int main(void)
 				push(printed);
 			} else if (!strcmp(s, "mc")) {
 				clearMemory();
-				peak = 1;
 			} else if (!mathfunction(s))
 				printf("error: unknown command %s\n", s);
 			break;
@@ -250,13 +241,13 @@ int main(void)
 			else
 				printf("error: zero divisor\n");
 			break;
-		case '!':
-			peak = 1;
+		case '?':
+			printTOP();
 			break;
-		case '#':
+		case 'd':
 			duplicateTop();
 			break;
-		case '&':
+		case 's':
 			swapTopTwo();
 			break;
 		case '~':
@@ -266,11 +257,7 @@ int main(void)
 			storeVariable();
 			break;
 		case '\n':
-			if (peak) {
-				printTOP();
-				peak = 0;
-			} else
-				printf("\t%.8g\n", printed = pop());
+			printf("\t%.8g\n", printed = pop());
 			break;
 		default:
 			if (islower(type))