From ba80acb1168a4adc6e67f6cc85133714ba2ccd1f Mon Sep 17 00:00:00 2001
From: Sam Anthony <sam@samanthony.xyz>
Date: Tue, 25 Jun 2024 16:27:44 -0400
Subject: logarithm functions

---
 func.go | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/func.go b/func.go
index bc8a0bc..d0cd11e 100644
--- a/func.go
+++ b/func.go
@@ -20,6 +20,12 @@ func parseFunction(fn string) func(*Calculator) {
 		return fac
 	case "ch": // choose
 		return combination
+	case "log10":
+		return log10
+	case "log2":
+		return log2
+	case "ln":
+		return ln
 	}
 	return nil
 }
@@ -150,6 +156,33 @@ func factorial(n uint) uint {
 	return n
 }
 
+// decimal logarithm.
+func log10(c *Calculator) {
+	x, err := c.stack.pop()
+	if err != nil {
+		return
+	}
+	c.stack.push(math.Log10(x))
+}
+
+// binary logarithm.
+func log2(c *Calculator) {
+	x, err := c.stack.pop()
+	if err != nil {
+		return
+	}
+	c.stack.push(math.Log2(x))
+}
+
+// natural logarithm.
+func ln(c *Calculator) {
+	x, err := c.stack.pop()
+	if err != nil {
+		return
+	}
+	c.stack.push(math.Log(x))
+}
+
 func isUint(n float64) bool {
 	return float64(uint(n)) == n
 }
-- 
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