make pow not return nan for negative numbers

Author: frostice482

big-num/omeganum.lua

@@ -662,11 +662,16 @@ function Big:pow(other)
     end
 
     if (self.number < 0) then
+        -- talisman-specific behavior
+        local p = self:abs():pow(other)
+        return other.number % 2 < 1 and p:neg() or p
+
+        --[[
         local mod = other.number % 2
         if mod ~= 0 and mod ~= 1 then return B.NaN end
-
         local p = self:abs():pow(other)
         return mod == 1 and p:neg() or p
+        ]]
     end
     if (self.number == 0) then
         return B.ZERO