Fix syntax of powint.dana

Use"=" instead of "==" for equality and moved "var temp is int"
declaration to the beginning of the block. The program still contains a
semantic error so I copied it to the dana/programs-erroneous directory.

Author: orestis42

dana/programs-erroneous/powint-erroneous.dana

@@ -0,0 +1,30 @@
+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
+    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
+
+  var b   is int
+  var e   is int
+  var m   is int
+  var res is int
+
+  b := readInteger()
+  e := readInteger()
+  m := readInteger()
+
+  powint: b, e, m, res
+
+  writeInteger: res
+  writeString: "\n"

dana/programs/powint.dana

@@ -3,17 +3,16 @@ 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
     else:
-      if exp % 2 == 0:
-        var temp is int
-        powint: base, exp / 2, mod, temp
+      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:
-        var temp is int
-        powint: base, exp - 1, mod, temp
+        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
 
   var b   is int