Module:Rational: Difference between revisions

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@@ Line 441: / Line 441: @@
 	end
 	return true
+end
+-- determine whether a rational number is an integer power of another rational number
+function p.is_power(a)
+	if type(a) == 'number' then
+		a = p.new(a)
+	end
+	if a.nan or a.inf or a.zero then
+		return false
+	end
+	if p.eq(a, 1) or p.eq(a, -1) then
+		return false
+	end
+	local function gcd(x, y)
+		if x < y then
+			x, y = y, x
+		end
+		while y > 0 do
+			x, y = y, x % y
+		end
+		return x
+	end
+	local total_power = nil
+	for factor, power in pairs(a) do
+		if type(factor) == 'number' then
+			if total_power then
+				total_power = gcd(total_power, math.abs(power))
+			else
+				total_power = math.abs(power)
+			end
+		end
+	end
+	return total_power > 1
 end