Update variables.c

Fix unprivelaged variable getting that prints bizarre values of variables that haven't been yet assigned. Previously, if you typed 'b' or another variable and pressed enter, it would output some exponential number like 1.23e-142 if you didn't assign that variable before. This fix prevents that by comparing varindex with the index of the current variable VARGET is checking for.

Author: sadeem-albir

chapter_4/exercise_4_06/variables.c

@@ -94,24 +94,24 @@ int main(void)
     case '~':
       push(sin(pop()));
       break;
-
-    case 'e':
+// Be sure to make the commands capitalized not to overlap them with variables, or vice versa according to personal preference
+    case 'E':
       push(exp(pop()));
       break;
 
-    case 'h':
+    case 'H':
       view_head();
       break;
 
-    case 'd':
+    case 'D':
       duplicate();
       break;
 
-    case 's':
+    case 'S':
       swap();
       break;
 
-    case 'c':
+    case 'C':
       clear();
       break;
 
@@ -121,7 +121,14 @@ int main(void)
       break;
 
     case VARGET:
-      push(var_buff[var - 'a']);
+      if (var - 'a' <= (varindex - 1)) // Check if the variable has been assigned previously
+      {
+        push(var_buff[var - 'a']);
+      }
+      else
+      {
+        printf("Error: undefined variable.\n");
+      }
       break;
 
     case '\n':
@@ -244,7 +251,7 @@ int getop(char s[])
 
   s[1] = '\0';
 
-  if (isalpha(c))
+  if (isalpha(c) && !isupper(c))
   {
     var = c;
     return VARGET;