From 3908de65f948aaf3662e566b1ea23e1618782c11 Mon Sep 17 00:00:00 2001
From: Jan Kadel <jan.kadel13@gmail.com>
Date: Sat, 24 May 2025 18:21:39 +0200
Subject: [PATCH] add floor and ceil methods

---
 fixed.go      | 62 ++++++++++++++++++++++++++++++++++++++++
 fixed_test.go | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 140 insertions(+)

diff --git a/fixed.go b/fixed.go
index 5a90421..5f9c301 100644
--- a/fixed.go
+++ b/fixed.go
@@ -273,6 +273,68 @@ func (f Fixed) Round(n int) Fixed {
 	return Fixed{fp: fp}
 }
 
+func (f Fixed) Floor(n int) Fixed {
+	if f.IsNaN() {
+		return NaN
+	}
+
+	if n >= nPlaces {
+		// If n is greater or equal nPlaces, we would integer-divide
+		// fraction by zero, which is not possible and also not required
+		// as if f had fractions they are already represented up until the nPlaces-th decimal
+		// (in this case 8th decimal)
+		return f
+	}
+
+	if n == 0 {
+		intpart := f.fp / scale
+		if f.fp < 0 && f.fp%scale != 0 {
+			intpart--
+		}
+		return Fixed{fp: intpart * scale}
+	}
+
+	fraction := f.fp % scale
+	f0 := fraction / int64(math.Pow10(nPlaces-n-1))
+	if f.fp < 0 {
+		f0 += 1 * sign(f.fp)
+	}
+	f0 = (f0 / 10)
+	f0 = f0 * int64(math.Pow10(nPlaces-n))
+
+	intpart := f.fp - fraction
+	fp := intpart + f0
+
+	return Fixed{fp: fp}
+}
+
+func (f Fixed) Ceil(n int) Fixed {
+	if f.IsNaN() {
+		return NaN
+	}
+
+	if n >= nPlaces {
+		// If n is greater or equal nPlaces, we would integer-divide
+		// fraction by zero, which is not possible and also not required
+		// as if f had fractions they are already represented up until the nPlaces-th decimal
+		// (in this case 8th decimal)
+		return f
+	}
+
+	fraction := f.fp % scale
+	f0 := fraction / int64(math.Pow10(nPlaces-n-1))
+	f0 = (f0 / 10)
+	if f.fp > 0 {
+		f0 += 1
+	}
+	f0 = f0 * int64(math.Pow10(nPlaces-n))
+
+	intpart := f.fp - fraction
+	fp := intpart + f0
+
+	return Fixed{fp: fp}
+}
+
 // Equal returns true if the f == f0. If either operand is NaN, false is returned. Use IsNaN() to test for NaN
 func (f Fixed) Equal(f0 Fixed) bool {
 	if f.IsNaN() || f0.IsNaN() {
diff --git a/fixed_test.go b/fixed_test.go
index d6633a4..b9b6336 100644
--- a/fixed_test.go
+++ b/fixed_test.go
@@ -552,6 +552,84 @@ func TestRound(t *testing.T) {
 	if f1.String() != "0.00000008" {
 		t.Error("should be equal", f1, "0.00000008")
 	}
+
+	f0 = NewS("0.333")
+	f1 = f0.Round(8)
+
+	if f1.String() != "0.333" {
+		t.Error("should be equal", f1, "0.333")
+	}
+
+	f0 = NewS("22.333")
+	f1 = f0.Round(0)
+
+	if f1.String() != "22" {
+		t.Error("should be equal", f1, "22")
+	}
+}
+
+func TestFloor(t *testing.T) {
+	f0 := NewS("22.399")
+	f1 := f0.Floor(0)
+	require.Equal(t, "22", f1.String())
+	f1 = f0.Floor(1)
+	require.Equal(t, "22.3", f1.String())
+	f1 = f0.Floor(2)
+	require.Equal(t, "22.39", f1.String())
+
+	f0 = NewS("-0.79")
+	f1 = f0.Floor(0)
+	require.Equal(t, "-1", f1.String())
+
+	f0 = NewS("-123.79")
+	f1 = f0.Floor(0)
+	require.Equal(t, "-124", f1.String())
+
+	f0 = NewS("-0.00000008")
+	f1 = f0.Floor(8)
+	require.Equal(t, "-0.00000008", f1.String())
+
+	f0 = NewS("0.00000008")
+	f1 = f0.Floor(8)
+	require.Equal(t, "0.00000008", f1.String())
+
+	f0 = NewS("-0.0000008")
+	f1 = f0.Floor(8)
+	require.Equal(t, "-0.0000008", f1.String())
+
+	f0 = NewS("0.0000008")
+	f1 = f0.Floor(8)
+	require.Equal(t, "0.0000008", f1.String())
+
+	f0 = NewS("-0.0000008")
+	f1 = f0.Floor(6)
+	require.Equal(t, "0", f1.String())
+
+	f0 = NewS("0.0000008")
+	f1 = f0.Floor(6)
+	require.Equal(t, "0", f1.String())
+}
+
+func TestCeil(t *testing.T) {
+	f0 := NewS("22.399")
+	f1 := f0.Ceil(0)
+	require.Equal(t, "23", f1.String())
+	f1 = f0.Ceil(1)
+	require.Equal(t, "22.4", f1.String())
+	f1 = f0.Ceil(2)
+	require.Equal(t, "22.4", f1.String())
+
+	f0 = NewS("22.329")
+	f1 = f0.Ceil(2)
+	require.Equal(t, "22.33", f1.String())
+
+	f0 = NewS("-0.0000008")
+	f1 = f0.Ceil(6)
+	require.Equal(t, "0", f1.String())
+
+	f0 = NewS("0.0000008")
+	f1 = f0.Ceil(6)
+	require.Equal(t, "0.000001", f1.String())
 }
 
 func TestEncodeDecode(t *testing.T) {