From 93a3cd98675e477a4614356297fcd20b95bfba8d Mon Sep 17 00:00:00 2001
From: david <SE.David@protonmail.com>
Date: Tue, 21 Jun 2022 20:47:50 +0300
Subject: [PATCH 1/3] Add NewFromBigRat function

---
 decimal.go      | 19 +++++++++++++++++++
 decimal_test.go | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+)

diff --git a/decimal.go b/decimal.go
index c614ea7..a025bdb 100644
--- a/decimal.go
+++ b/decimal.go
@@ -125,6 +125,25 @@ func NewFromBigInt(value *big.Int, exp int32) Decimal {
 	}
 }
 
+// NewFromBigRat returns a new Decimal from a big.Rat. The nominator and
+// denominator are divided and rounded to the given precision.
+//
+// Example:
+//
+//     d1, err := NewFromBigRat(big.NewRat(0, 1), 4)
+//     d2, err := NewFromBigRat(big.NewRat(4, 5), 100)
+//     d3, err := NewFromBigRat(big.NewRat(10000, 3), 300)
+//
+func NewFromBigRat(value *big.Rat, precision int32) Decimal {
+	return Decimal{
+		value: new(big.Int).Set(value.Num()),
+		exp:   0,
+	}.DivRound(Decimal{
+		value: new(big.Int).Set(value.Denom()),
+		exp:   0,
+	}, precision)
+}
+
 // NewFromString returns a new Decimal from a string representation.
 // Trailing zeroes are not trimmed.
 //
diff --git a/decimal_test.go b/decimal_test.go
index 2b3a99e..f9b964a 100644
--- a/decimal_test.go
+++ b/decimal_test.go
@@ -556,6 +556,51 @@ func TestNewFromBigIntWithExponent(t *testing.T) {
 	}
 }
 
+func TestNewFromBigRat(t *testing.T) {
+	mustParseRat := func(val string) *big.Rat {
+		num, _ := new(big.Rat).SetString(val)
+		return num
+	}
+
+	type Inp struct {
+		val  *big.Rat
+		prec int32
+	}
+
+	tests := map[Inp]string{
+		Inp{big.NewRat(0, 1), 16}:                                                     "0",
+		Inp{big.NewRat(4, 5), 16}:                                                     "0.8",
+		Inp{big.NewRat(10, 2), 16}:                                                    "5",
+		Inp{big.NewRat(1023427554493, 43432632), 16}:                                  "23563.5628642767953828", // rounded
+		Inp{big.NewRat(1, 434324545566634), 16}:                                       "0.0000000000000023",
+		Inp{big.NewRat(1, 3), 16}:                                                     "0.3333333333333333",
+		Inp{big.NewRat(2, 3), 2}:                                                      "0.67",               // rounded
+		Inp{big.NewRat(2, 3), 16}:                                                     "0.6666666666666667", // rounded
+		Inp{big.NewRat(10000, 3), 16}:                                                 "3333.3333333333333333",
+		Inp{mustParseRat("30702832066636633479"), 16}:                                 "30702832066636633479",
+		Inp{mustParseRat("487028320159896636679.1827512895753"), 16}:                  "487028320159896636679.1827512895753",
+		Inp{mustParseRat("127028320612589896636633479.173582751289575278357832"), -2}: "127028320612589896636633500",                  // rounded
+		Inp{mustParseRat("127028320612589896636633479.173582751289575278357832"), 16}: "127028320612589896636633479.1735827512895753", // rounded
+		Inp{mustParseRat("127028320612589896636633479.173582751289575278357832"), 32}: "127028320612589896636633479.173582751289575278357832",
+	}
+
+	// add negatives
+	for p, s := range tests {
+		if p.val.Cmp(new(big.Rat)) > 0 {
+			tests[Inp{p.val.Neg(p.val), p.prec}] = "-" + s
+		}
+	}
+
+	for input, s := range tests {
+		d := NewFromBigRat(input.val, input.prec)
+		if d.String() != s {
+			t.Errorf("expected %s, got %s (%s, %d)",
+				s, d.String(),
+				d.value.String(), d.exp)
+		}
+	}
+}
+
 func TestCopy(t *testing.T) {
 	origin := New(1, 0)
 	cpy := origin.Copy()

From f3eac4fb6504eb4c706bd4f71a0362bf9858d11a Mon Sep 17 00:00:00 2001
From: david <SE.David@protonmail.com>
Date: Tue, 21 Jun 2022 21:09:28 +0300
Subject: [PATCH 2/3] Fix numerator typo

---
 decimal.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/decimal.go b/decimal.go
index a025bdb..c833a97 100644
--- a/decimal.go
+++ b/decimal.go
@@ -125,7 +125,7 @@ func NewFromBigInt(value *big.Int, exp int32) Decimal {
 	}
 }
 
-// NewFromBigRat returns a new Decimal from a big.Rat. The nominator and
+// NewFromBigRat returns a new Decimal from a big.Rat. The numerator and
 // denominator are divided and rounded to the given precision.
 //
 // Example:

From acffc5529c28a1baa0de07c251fee158df882f52 Mon Sep 17 00:00:00 2001
From: david <dovb@jellydator.dev>
Date: Sun, 18 Feb 2024 14:54:26 +0200
Subject: [PATCH 3/3] adjust comment

---
 decimal.go | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/decimal.go b/decimal.go
index c833a97..117fbe9 100644
--- a/decimal.go
+++ b/decimal.go
@@ -130,9 +130,10 @@ func NewFromBigInt(value *big.Int, exp int32) Decimal {
 //
 // Example:
 //
-//     d1, err := NewFromBigRat(big.NewRat(0, 1), 4)
-//     d2, err := NewFromBigRat(big.NewRat(4, 5), 100)
-//     d3, err := NewFromBigRat(big.NewRat(10000, 3), 300)
+//     d1 := NewFromBigRat(big.NewRat(0, 1), 0)    // output: "0"
+//     d2 := NewFromBigRat(big.NewRat(4, 5), 1)    // output: "0.8"
+//     d3 := NewFromBigRat(big.NewRat(1000, 3), 3) // output: "333.333"
+//     d4 := NewFromBigRat(big.NewRat(2, 7), 4)    // output: "0.2857"
 //
 func NewFromBigRat(value *big.Rat, precision int32) Decimal {
 	return Decimal{