Bugfix: #57 Powers of -1 for integers over Number.MAX_SAFE_INTEGER

decimal.es6.js

@@ -2281,6 +2281,11 @@ P.toPower = P.pow = function (y) {
   // Result is negative if x is negative and the last digit of integer y is odd.
   sign = sign < 0 && y.d[Math.max(e, k)] & 1 ? -1 : 1;
 
+  if (x.eq(-1)) {
+    x.s = sign;
+    return x;
+  }
+
   // Estimate result exponent.
   // x^y = 10^e,  where e = y * log10(x)
   // log10(x) = log10(x_significand) + x_exponent

decimal.js

@@ -2283,11 +2283,17 @@
     // Result is negative if x is negative and the last digit of integer y is odd.
     sign = sign < 0 && y.d[Math.max(e, k)] & 1 ? -1 : 1;
 
+    if (x.eq(-1)) {
+      x.s = sign;
+      return x;
+    }
+
     // Estimate result exponent.
     // x^y = 10^e,  where e = y * log10(x)
     // log10(x) = log10(x_significand) + x_exponent
     // log10(x_significand) = ln(x_significand) / ln(10)
     k = mathpow(+x, yn);
+
     e = k == 0 || !isFinite(k)
       ? mathfloor(yn * (Math.log('0.' + digitsToString(x.d)) / Math.LN10 + x.e + 1))
       : new Ctor(k + '').e;