add support for negative decimal exponents

src/exponent.c

@@ -30,12 +30,15 @@ double expIN(double e, double num){
         else{
             return  (1.0 / expI((e*-1), num));
         }   
-    }else{
+    }else if(num > 0.0){
         if(e>0.0){
             return exponential(e*logN(num, 0.00000001));
         }
+        else{
+            return (1.0 / exponential((-1*e)*logN(num, 0.00000001)));
+        }
     }
-    return 0;
+    return -1;
 }
 
 unsigned long long fac(int x){