From 5d759f2deab8f7837b74d800525729624c5b7e80 Mon Sep 17 00:00:00 2001
From: Sadeep Madurange <smadurange@users.noreply.github.com>
Date: Mon, 13 Dec 2021 19:57:34 +0800
Subject: 4.10

---
 4/10.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 90 insertions(+), 4 deletions(-)

diff --git a/4/10.c b/4/10.c
index 00ad493..df12ab1 100644
--- a/4/10.c
+++ b/4/10.c
@@ -1,9 +1,12 @@
 #include <ctype.h>
+#include <math.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #define MAXOP 100
 #define MAXLINE 1000
+#define HEIGHT 1000
 
 #define NUM '0'
 #define FUN '1'
@@ -14,9 +17,10 @@ void push(double);
 double peek();
 double pop();
 void clear();
+double vartoval(char);
 
 int main(int argc, char *argv[]) {
-  int type;
+  int type, op1, op2;
   char s[MAXOP];
 
   printf("Press CTRL+C to exit\n");
@@ -24,16 +28,58 @@ int main(int argc, char *argv[]) {
   while (type == getop(s)) {
     switch (type) {
     case NUM:
+      push(atof(s));
       break;
     case '+':
+      op1 = pop();
+      op2 = pop();
+      if (isalpha(op1))
+        op1 = vartoval(op1);
+      if (isalpha(op2))
+        op2 = vartoval(op2);
+      push(op1 + op2);
       break;
     case '-':
+      op1 = pop();
+      op2 = pop();
+      if (isalpha(op1))
+        op1 = vartoval(op1);
+      if (isalpha(op2))
+        op2 = vartoval(op2);
+      push(op1 - op2);
       break;
     case '*':
+      op1 = pop();
+      op2 = pop();
+      if (isalpha(op1))
+        op1 = vartoval(op1);
+      if (isalpha(op2))
+        op2 = vartoval(op2);
+      push(op1 * op2);
       break;
     case '/':
+      op1 = pop();
+      op2 = pop();
+      if (isalpha(op1))
+        op1 = vartoval(op1);
+      if (isalpha(op2))
+        op2 = vartoval(op2);
+      if (op1 == 0.0)
+        printf("error: division by zero\n");
+      else
+        push((double)op2 / op1);
       break;
     case '%':
+      op1 = pop();
+      op2 = pop();
+      if (isalpha(op1))
+        op1 = vartoval(op1);
+      if (isalpha(op2))
+        op2 = vartoval(op2);
+      if (op1 == 0.0)
+        printf("error: division by zero\n");
+      else
+        push((int)op2 % (int)op1);
       break;
     case '=':
       break;
@@ -52,10 +98,10 @@ int line[MAXLINE];
 
 void mgetline() {
   int i, c;
-  
+
   for (i = 0; i < MAXLINE - 1 && (c = getchar()) != '\n' && c != EOF; i++) {
     line[i] = c;
-  } 
+  }
   line[i] = 0;
   ptr = 0;
 }
@@ -66,7 +112,7 @@ int getop(char s[]) {
   if (line[ptr] == 0)
     mgetline();
 
-  // get next token 
+  // get next token
   for (i = 0; i < MAXOP - 1 && (c = line[ptr]) != ' ' && c != 0; i++, ptr++)
     s[i] = c;
   s[i] = 0;
@@ -81,5 +127,45 @@ int getop(char s[]) {
       return s[0];
   }
 
+  if (i > 1 && (isdigit(s[0]) || s[0] == '-' && isdigit(s[1])))
+    return NUM;
+
+  // last printed variable
+  if (strcmp("LOUT", s) == 0)
+    return VAR;
+
   return FUN;
+}
+
+int sp = 0;
+double stack[HEIGHT];
+
+void push(double f) {
+  if (sp < HEIGHT)
+    stack[sp++] = f;
+  else
+    printf("error: stack empty\n");
+}
+
+double pop() {
+  if (sp > 0)
+    return stack[--sp];
+  else {
+    printf("error: stack empty\n");
+    return 0.0;
+  }
+}
+
+double peek() {
+  if (sp > 0)
+    return stack[sp - 1];
+  else {
+    printf("error: stack empty\n");
+    return 0.0;
+  }
+}
+
+void clear() {
+  for (; sp > 0; sp--)
+    ;
 }
\ No newline at end of file
-- 
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