feat(bpmath): MulDec (#2166)

* feat(bpmath): MulDec

* changelog

CHANGELOG.md

@@ -52,6 +52,8 @@ Ref: https://keepachangelog.com/en/1.0.0/
 - [2146](https://github.com/umee-network/umee/pull/2146) Add store `GetTimeMs` and `SetTimeMs`.
 - [2157](https://github.com/umee-network/umee/pull/2157) Add `x/metoken` module.
 - [2145](https://github.com/umee-network/umee/pull/2145) Add hard market cap for token emission.
+- [2155](https://github.com/umee-network/umee/pull/2155) `bpmath`: basis points math package.
+- [2166](https://github.com/umee-network/umee/pull/2166) Basis Points: `MulDec`
 
 ### Improvements
 

util/bpmath/bp.go

@@ -20,6 +20,11 @@ func (bp BP) Mul(a cmath.Int) cmath.Int {
 	return Mul(a, bp)
 }
 
+// MulDec return a*bp rounding towards zero.
+func (bp BP) MulDec(a sdk.Dec) sdk.Dec {
+	return MulDec(a, bp)
+}
+
 // FromQuo returns a/b in basis points.
 // Contract: a>=0 and b > 0.
 // Panics if a/b >= MaxUint32/10'000 or if b==0.
@@ -44,7 +49,7 @@ func quo(a, b cmath.Int, rounding Rounding, max uint64) uint64 {
 
 // Mul returns a * b_basis_points rounding towards zero.
 // Contract: b in [0, MaxUint32]
-func Mul[T BP | FixedBP](a cmath.Int, b T) cmath.Int {
+func Mul[T BP | FixedBP | int](a cmath.Int, b T) cmath.Int {
 	if b == 0 {
 		return cmath.ZeroInt()
 	}
@@ -53,3 +58,15 @@ func Mul[T BP | FixedBP](a cmath.Int, b T) cmath.Int {
 	}
 	return a.MulRaw(int64(b)).Quo(oneBigInt)
 }
+
+// MulDec returns a * b_basis_points rounding towards zero.
+// Contract: b in [0, MaxUint32]
+func MulDec[T BP | FixedBP | int](a sdk.Dec, b T) sdk.Dec {
+	if b == 0 {
+		return sdk.ZeroDec()
+	}
+	if b == One {
+		return a
+	}
+	return a.MulInt64(int64(b)).Quo(oneDec)
+}

util/bpmath/bp_test.go

@@ -56,3 +56,26 @@ func TestInt(t *testing.T) {
 	si = sdk.NewInt(-1201)
 	require.Equal(bp.Mul(si), sdk.NewInt(-12))
 }
+
+func TestBPMulDec(t *testing.T) {
+	t.Parallel()
+	require := require.New(t)
+
+	bp := BP(1000)
+	bp2 := BP(1)
+	bp3 := BP(5000)
+	bp4 := BP(20000)
+	d := sdk.MustNewDecFromStr("12.5002")
+	d2 := sdk.NewDec(10000)
+	d3 := sdk.NewDec(1000)
+
+	require.Equal(d, MulDec(d, One))
+	require.Equal(sdk.ZeroDec(), MulDec(d, Zero))
+	require.Equal(sdk.OneDec(), bp2.MulDec(d2))
+	require.Equal(sdk.MustNewDecFromStr("0.1"), bp2.MulDec(d3))
+
+	require.Equal(sdk.MustNewDecFromStr("1.25002"), bp.MulDec(d))
+	require.Equal(sdk.MustNewDecFromStr("0.00125002"), bp2.MulDec(d))
+	require.Equal(sdk.MustNewDecFromStr("6.2501"), bp3.MulDec(d))
+	require.Equal(sdk.MustNewDecFromStr("25.0004"), bp4.MulDec(d))
+}

util/bpmath/fixed_bp.go

@@ -24,3 +24,8 @@ func (bp FixedBP) ToDec() sdk.Dec {
 func (bp FixedBP) Mul(a math.Int) math.Int {
 	return Mul(a, bp)
 }
+
+// MulDec return a*bp rounding towards zero.
+func (bp FixedBP) MulDec(a sdk.Dec) sdk.Dec {
+	return MulDec(a, bp)
+}

util/bpmath/fixed_bp_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"cosmossdk.io/math"
+	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/stretchr/testify/require"
 )
 
@@ -107,3 +108,26 @@ func TestFixedToDec(t *testing.T) {
 		require.Equal(tc.exp.String(), bp.String(), fmt.Sprint("test-bp ", tc.name))
 	}
 }
+
+func TestFixedBPMulDec(t *testing.T) {
+	t.Parallel()
+	require := require.New(t)
+
+	bp := FixedBP(1000)
+	bp2 := FixedBP(1)
+	bp3 := FixedBP(5000)
+	bp4 := FixedBP(20000)
+	d := sdk.MustNewDecFromStr("12.5002")
+	d2 := sdk.NewDec(10000)
+	d3 := sdk.NewDec(1000)
+
+	require.Equal(d, MulDec(d, One))
+	require.Equal(sdk.ZeroDec(), MulDec(d, Zero))
+	require.Equal(sdk.OneDec(), bp2.MulDec(d2))
+	require.Equal(sdk.MustNewDecFromStr("0.1"), bp2.MulDec(d3))
+
+	require.Equal(sdk.MustNewDecFromStr("1.25002"), bp.MulDec(d))
+	require.Equal(sdk.MustNewDecFromStr("0.00125002"), bp2.MulDec(d))
+	require.Equal(sdk.MustNewDecFromStr("6.2501"), bp3.MulDec(d))
+	require.Equal(sdk.MustNewDecFromStr("25.0004"), bp4.MulDec(d))
+}

util/bpmath/types.go

@@ -2,6 +2,7 @@ package bpmath
 
 import (
 	"cosmossdk.io/math"
+	sdk "github.com/cosmos/cosmos-sdk/types"
 )
 
 type Rounding uint
@@ -14,6 +15,8 @@ const (
 const (
 	One  = 10000
 	Half = One / 2
+	Zero = 0
 )
 
 var oneBigInt = math.NewIntFromUint64(One)
+var oneDec = sdk.NewDec(One)