From 7e1c45ab44be3c2a3a10716ced8818f2004be45f Mon Sep 17 00:00:00 2001
From: CC <jeff@chipnetics.com>
Date: Sat, 9 Jul 2022 01:41:58 -0600
Subject: [PATCH] math: add round_sig function for f64 (#14997)

---
 vlib/math/floor.v     | 29 +++++++++++++++++++++++++++++
 vlib/math/math_test.v | 11 +++++++++++
 2 files changed, 40 insertions(+)

diff --git a/vlib/math/floor.v b/vlib/math/floor.v
index a2c3208e3c..bfaf6607e2 100644
--- a/vlib/math/floor.v
+++ b/vlib/math/floor.v
@@ -75,6 +75,35 @@ pub fn round(x f64) f64 {
 	return y
 }
 
+// Returns the rounded float, with sig_digits of precision.
+// i.e `assert round_sig(4.3239437319748394,6) == 4.323944`
+pub fn round_sig(x f64, sig_digits int) f64 {
+	mut ret_str := '$x'
+
+	match sig_digits {
+		0 { ret_str = '${x:0.0f}' }
+		1 { ret_str = '${x:0.1f}' }
+		2 { ret_str = '${x:0.2f}' }
+		3 { ret_str = '${x:0.3f}' }
+		4 { ret_str = '${x:0.4f}' }
+		5 { ret_str = '${x:0.5f}' }
+		6 { ret_str = '${x:0.6f}' }
+		7 { ret_str = '${x:0.7f}' }
+		8 { ret_str = '${x:0.8f}' }
+		9 { ret_str = '${x:0.9f}' }
+		10 { ret_str = '${x:0.10f}' }
+		11 { ret_str = '${x:0.11f}' }
+		12 { ret_str = '${x:0.12f}' }
+		13 { ret_str = '${x:0.13f}' }
+		14 { ret_str = '${x:0.14f}' }
+		15 { ret_str = '${x:0.15f}' }
+		16 { ret_str = '${x:0.16f}' }
+		else { ret_str = '$x' }
+	}
+
+	return ret_str.f64()
+}
+
 // round_to_even returns the nearest integer, rounding ties to even.
 //
 // special cases are:
diff --git a/vlib/math/math_test.v b/vlib/math/math_test.v
index fc2d16cd17..93cf6792ef 100644
--- a/vlib/math/math_test.v
+++ b/vlib/math/math_test.v
@@ -808,6 +808,17 @@ fn test_round() {
 	}
 }
 
+fn fn_test_round_sig() {
+	assert round_sig(4.3239437319748394, -1) == 4.3239437319748394
+	assert round_sig(4.3239437319748394, 0) == 4.0000000000000000
+	assert round_sig(4.3239437319748394, 1) == 4.3000000000000000
+	assert round_sig(4.3239437319748394, 2) == 4.3200000000000000
+	assert round_sig(4.3239437319748394, 3) == 4.3240000000000000
+	assert round_sig(4.3239437319748394, 6) == 4.3239440000000000
+	assert round_sig(4.3239437319748394, 12) == 4.323943731975
+	assert round_sig(4.3239437319748394, 17) == 4.3239437319748394
+}
+
 fn test_sin() {
 	for i := 0; i < math.vf_.len; i++ {
 		f := sin(math.vf_[i])