From 42557bcfc47cd00012a6a559c2b002fffa245b7d Mon Sep 17 00:00:00 2001
From: Sam Anthony <sam@samanthony.xyz>
Date: Tue, 25 Jun 2024 16:53:08 -0400
Subject: remove factorial wrapper function

---
 func.go | 36 ++++++++++++++----------------------
 1 file changed, 14 insertions(+), 22 deletions(-)

diff --git a/func.go b/func.go
index e3bb8d7..fc19e87 100644
--- a/func.go
+++ b/func.go
@@ -17,7 +17,12 @@ func parseFunction(fn string) func(*Calculator) {
 	case "rad":
 		return apply(degToRad)
 	case "fac":
-		return fac
+		return apply(func(x float64) float64 {
+			if !isUint(x) {
+				return x
+			}
+			return float64(factorial(uint(x)))
+		})
 	case "ch": // choose
 		return combination
 	case "log10":
@@ -99,17 +104,16 @@ func radToDeg(rad float64) (deg float64) {
 	return rad * 180 / math.Pi
 }
 
-// Factorial (!).
-func fac(c *Calculator) {
-	n, err := c.stack.pop()
-	if err != nil {
-		return
+// factorial returns n! (n factorial).
+func factorial(n uint) uint {
+	if n == 0 {
+		return 1
 	}
-	if !isUint(n) { // undefined on non-ints
-		c.stack.push(n)
-		return
+	// n! = n*(n-1)!
+	for i := n - 1; i > 1; i-- {
+		n *= i
 	}
-	c.stack.push(float64(factorial(uint(n))))
+	return n
 }
 
 // Combination function. "n choose k" with integers n and k such that n >= k >= 0.
@@ -142,18 +146,6 @@ func combination(c *Calculator) {
 	}
 }
 
-// factorial returns n! (n factorial).
-func factorial(n uint) uint {
-	if n == 0 { // 0! = 1
-		return 1
-	}
-	// n! = n*(n-1)!
-	for i := n - 1; i > 1; i-- {
-		n *= i
-	}
-	return n
-}
-
 func isUint(n float64) bool {
 	return float64(uint(n)) == n
 }
-- 
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