From 3e331d4cf0b05f1983e760e397a400456ead9e4b Mon Sep 17 00:00:00 2001
From: Mike <tankf33der@disroot.org>
Date: Thu, 22 Jan 2026 21:52:06 +0200
Subject: [PATCH] math: rewrite hypot(), update tests (#26418)

---
 vlib/math/hypot.v     | 34 ++++++++++++++++++----------------
 vlib/math/math_test.v |  5 +++--
 2 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/vlib/math/hypot.v b/vlib/math/hypot.v
index f4200bdde..3fecd9816 100644
--- a/vlib/math/hypot.v
+++ b/vlib/math/hypot.v
@@ -1,25 +1,27 @@
 module math
 
-// hypot returns the hypotenuse of the triangle give two sides
+// hypot returns the hypotenuse of the triangle give two sides.
+//
+// special cases are:
+// hypot(±inf, y) = +inf
+// hypot(x, ±inf) = +inf
+// hypot(nan, y) = nan
+// hypot(x, nan) = nan
 pub fn hypot(x f64, y f64) f64 {
-	if is_inf(x, 0) || is_inf(y, 0) {
+	mut p := abs(x)
+	mut q := abs(y)
+	if is_inf(p, 1) || is_inf(q, 1) {
 		return inf(1)
 	}
-	if is_nan(x) || is_nan(y) {
+	if is_nan(p) || is_nan(q) {
 		return nan()
 	}
-	mut result := 0.0
-	if x != 0.0 || y != 0.0 {
-		abs_x := abs(x)
-		abs_y := abs(y)
-		cmin, cmax := minmax(abs_x, abs_y)
-		rat := cmin / cmax
-		root_term := sqrt(1.0 + rat * rat)
-		if cmax < max_f64 / root_term {
-			result = cmax * root_term
-		} else {
-			panic('overflow in hypot_e function')
-		}
+	if p < q {
+		p, q = q, p
 	}
-	return result
+	if p == 0.0 {
+		return 0.0
+	}
+	q = q / p
+	return p * sqrt(1 + q * q)
 }
diff --git a/vlib/math/math_test.v b/vlib/math/math_test.v
index ea7d9671f..88245d814 100644
--- a/vlib/math/math_test.v
+++ b/vlib/math/math_test.v
@@ -658,10 +658,11 @@ fn test_hypot() {
 		[inf(1), inf(-1)], [inf(1), 0], [inf(1), inf(1)], [inf(1),
 			nan()],
 		[nan(), inf(-1)], [nan(), 0], [nan(), inf(1)], [nan(),
-			nan()]]
+			nan()],
+		[-0.0, max_f64]]
 	hypot_sc_ := [inf(1), inf(1), inf(1), inf(1), 0, 0, 0, 0, inf(1),
 		inf(1), nan(), inf(1), inf(1), inf(1), inf(1), inf(1),
-		nan(), inf(1), nan()]
+		nan(), inf(1), nan(), max_f64]
 	for i := 0; i < vfhypot_sc_.len; i++ {
 		f := hypot(vfhypot_sc_[i][0], vfhypot_sc_[i][1])
 		assert alike(hypot_sc_[i], f)
-- 
2.39.5