[Dana]Fix powint-erroneous.dana

Add actual semantic error in powint-erroneous.dana and highlighted it
with a comment.

Author: orestis42

dana/programs-erroneous/powint-erroneous.dana

@@ -1,30 +1,37 @@
 def main
 
   def powint: base as int, exp as int, mod as int, result as ref int
-
-    base := base % mod
+    
     var temp is int
 
     if exp < 1:
       result := 1
+    elif exp = 0: 
+        result := 1
     else:
-      if exp % 2 = 0:
-        powint: base, exp / 2, mod, temp # SEMANTIC ERROR: temp is not a ref variable but being passed to a ref parameter
-        result := (temp * temp) % mod
-      else:
-        powint: base, exp - 1, mod, temp # SEMANTIC ERROR: temp is not a ref variable but being passed to a ref parameter
-        result := (base * temp) % mod
+      powint: base, exp / 2, mod, temp 
+      
+      if exp % 2 = 0: 
+        result := (temp * temp) % mod 
+      else: 
+        result := (base * temp * temp) % mod
+        
+        writeString: temp # SEMANTIC ERROR: Calling writeString (expects byte[]) with an int argument (temp)
 
   var b   is int
   var e   is int
   var m   is int
   var res is int
 
+  writeString: "Enter base: "
   b := readInteger()
+  writeString: "Enter exponent: "
   e := readInteger()
+  writeString: "Enter modulus: "
   m := readInteger()
 
   powint: b, e, m, res
 
+  writeString: "Result: "
   writeInteger: res
   writeString: "\n"