Merge pull request #14 from jon4hz/main

Fix ToSignificant() output on very small numbers

Author: miraclesu

entities/fraction.go

@@ -2,17 +2,18 @@ package entities
 
 import (
 	"math/big"
+	"strings"
 
 	"github.com/shopspring/decimal"
 
 	"github.com/miraclesu/uniswap-sdk-go/constants"
 	"github.com/miraclesu/uniswap-sdk-go/number"
 )
 
-var (
-	// ZeroFraction zero fraction instance
-	ZeroFraction = NewFraction(constants.Zero, nil)
-)
+// ZeroFraction zero fraction instance
+var ZeroFraction = NewFraction(constants.Zero, nil)
+
+const decimalSplitLength = 2
 
 // Fraction warps math franction
 type Fraction struct {
@@ -120,16 +121,31 @@ func (f *Fraction) Divide(other *Fraction) *Fraction {
 func (f *Fraction) ToSignificant(significantDigits uint, opt ...number.Option) string {
 	f.opts = number.New(number.WithGroupSeparator('\xA0'), number.WithRoundingMode(constants.RoundHalfUp))
 	f.opts.Apply(opt...)
-	f.opts.Apply(number.WithRoundingPrecision(int(significantDigits)))
 
 	d := decimal.NewFromBigInt(f.Numerator, 0).Div(decimal.NewFromBigInt(f.Denominator, 0))
+	if d.LessThan(decimal.New(1, 0)) {
+		significantDigits += countZerosAfterDecimalPoint(d.String())
+	}
+	f.opts.Apply(number.WithRoundingPrecision(int(significantDigits)))
 	if v, err := number.DecimalRound(d, f.opts); err == nil {
 		d = v
 	}
-
 	return number.DecimalFormat(d, f.opts)
 }
 
+func countZerosAfterDecimalPoint(d string) uint {
+	grp := strings.Split(d, ".")
+	if len(grp) != decimalSplitLength {
+		return 0
+	}
+	for i, v := range grp[1] {
+		if v != '0' {
+			return uint(i)
+		}
+	}
+	return 0
+}
+
 // ToFixed format output
 func (f *Fraction) ToFixed(decimalPlaces uint, opt ...number.Option) string {
 	f.opts = number.New(number.WithGroupSeparator('\xA0'), number.WithRoundingMode(constants.RoundHalfUp))

entities/fraction_test.go

@@ -6,7 +6,7 @@ import (
 )
 
 func TestQuotient(t *testing.T) {
-	var tests = []struct {
+	tests := []struct {
 		Input  [2]int64
 		Output int64
 	}{
@@ -23,7 +23,7 @@ func TestQuotient(t *testing.T) {
 }
 
 func TestRemainder(t *testing.T) {
-	var tests = []struct {
+	tests := []struct {
 		Input  [2]int64
 		Output [2]int64
 	}{
@@ -41,7 +41,7 @@ func TestRemainder(t *testing.T) {
 }
 
 func TestInvert(t *testing.T) {
-	var tests = []struct {
+	tests := []struct {
 		Input  [2]int64
 		Output [2]int64
 	}{
@@ -56,7 +56,7 @@ func TestInvert(t *testing.T) {
 }
 
 func TestAdd(t *testing.T) {
-	var tests = []struct {
+	tests := []struct {
 		Input  [4]int64
 		Output [2]int64
 	}{
@@ -75,7 +75,7 @@ func TestAdd(t *testing.T) {
 }
 
 func TestSubtract(t *testing.T) {
-	var tests = []struct {
+	tests := []struct {
 		Input  [4]int64
 		Output [2]int64
 	}{
@@ -94,7 +94,7 @@ func TestSubtract(t *testing.T) {
 }
 
 func TestLessThan(t *testing.T) {
-	var tests = []struct {
+	tests := []struct {
 		Input  [4]int64
 		Output bool
 	}{
@@ -112,7 +112,7 @@ func TestLessThan(t *testing.T) {
 }
 
 func TestEqualTo(t *testing.T) {
-	var tests = []struct {
+	tests := []struct {
 		Input  [4]int64
 		Output bool
 	}{
@@ -131,7 +131,7 @@ func TestEqualTo(t *testing.T) {
 }
 
 func TestGreaterThan(t *testing.T) {
-	var tests = []struct {
+	tests := []struct {
 		Input  [4]int64
 		Output bool
 	}{
@@ -151,7 +151,7 @@ func TestGreaterThan(t *testing.T) {
 }
 
 func TestMultiply(t *testing.T) {
-	var tests = []struct {
+	tests := []struct {
 		Input  [4]int64
 		Output [2]int64
 	}{
@@ -171,7 +171,7 @@ func TestMultiply(t *testing.T) {
 }
 
 func TestDivide(t *testing.T) {
-	var tests = []struct {
+	tests := []struct {
 		Input  [4]int64
 		Output [2]int64
 	}{
@@ -192,7 +192,7 @@ func TestDivide(t *testing.T) {
 }
 
 func TestToSignificant(t *testing.T) {
-	var tests = []struct {
+	tests := []struct {
 		Input  [2]int64
 		Output string
 		Format uint
@@ -203,6 +203,7 @@ func TestToSignificant(t *testing.T) {
 		{[2]int64{126, 100}, "1.26", 2},
 		{[2]int64{124, 100}, "1.2", 1},
 		{[2]int64{124, 100}, "1.24", 2},
+		{[2]int64{125, 1000000000}, "0.00000013", 2},
 	}
 	for i, test := range tests {
 		output := NewFraction(big.NewInt(test.Input[0]), big.NewInt(test.Input[1])).ToSignificant(test.Format)