hardcode decimal fractions (#27)

* split

* master

* fix

* fix

* fix

Author: nikolaydubina

.github/workflows/tests.yml

@@ -2,9 +2,9 @@ name: Test
 
 on:
   push:
-    branches: [main]
+    branches: [master]
   pull_request:
-    branches: [main]
+    branches: [master]
 
 permissions: read-all
 
@@ -15,7 +15,7 @@ jobs:
     steps:
       - name: Check outcode
         uses: actions/checkout@v4
-    
+
       - name: Set up Go 1.x
         uses: actions/setup-go@v5
         with:
@@ -27,6 +27,12 @@ jobs:
           go install github.com/jstemmer/go-junit-report/v2@latest
           go test -coverprofile=coverage.out -covermode=atomic -cover -json -v ./... 2>&1 | go-junit-report -set-exit-code > tests.xml
 
+      - name: Fuzz
+        run: |
+          go test -list . | grep Fuzz | xargs -P 8 -I {} go test -fuzz {} -fuzztime 5s .
+          cd fp3; go test -list . | grep Fuzz | xargs -P 8 -I {} go test -fuzz {} -fuzztime 5s . ; cd ..
+          cd fp6; go test -list . | grep Fuzz | xargs -P 8 -I {} go test -fuzz {} -fuzztime 5s . ; cd ..
+
       - name: Upload test results to Codecov
         uses: codecov/test-results-action@v1
         with:

fpdecimal.go fp3/fpdecimal.gofpdecimal.go renamed to fp3/fpdecimal.go

@@ -1,64 +1,62 @@
-package fpdecimal
+package fp3
 
-// Decimal is a decimal with fixed number of fraction digits.
-// By default, uses 3 fractional digits.
-// For example, values with 3 fractional digits will fit in ~9 quadrillion.
+import "github.com/nikolaydubina/fpdecimal"
+
+// Decimal with 3 fractional digits.
 // Fractions lower than that are discarded in operations.
 // Max: +9223372036854775.807
 // Min: -9223372036854775.808
 type Decimal struct{ v int64 }
 
 var Zero = Decimal{}
 
-var multipliers = [...]int64{1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000, 10000000000}
-
 type integer interface {
 	int | int8 | int16 | int32 | int64 | uint | uint8 | uint16 | uint32 | uint64
 }
 
-// FractionDigits that operations will use.
-// Warning, after change, existing variables are not updated.
-// Likely you want to use this once per runtime and in `func init()`.
-var FractionDigits uint8 = 3
+const (
+	fractionDigits = 3
+	multiplier     = 1000
+)
 
-func FromInt[T integer](v T) Decimal { return Decimal{int64(v) * multipliers[FractionDigits]} }
+func FromInt[T integer](v T) Decimal { return Decimal{int64(v) * multiplier} }
 
 func FromFloat[T float32 | float64](v T) Decimal {
-	return Decimal{int64(float64(v) * float64(multipliers[FractionDigits]))}
+	return Decimal{int64(float64(v) * float64(multiplier))}
 }
 
 // FromIntScaled expects value already scaled to minor units
 func FromIntScaled[T integer](v T) Decimal { return Decimal{int64(v)} }
 
 func FromString(s string) (Decimal, error) {
-	v, err := ParseFixedPointDecimal([]byte(s), FractionDigits)
+	v, err := fpdecimal.ParseFixedPointDecimal([]byte(s), fractionDigits)
 	return Decimal{v}, err
 }
 
 func (v *Decimal) UnmarshalJSON(b []byte) (err error) {
-	v.v, err = ParseFixedPointDecimal(b, FractionDigits)
+	v.v, err = fpdecimal.ParseFixedPointDecimal(b, fractionDigits)
 	return err
 }
 
 func (v Decimal) MarshalJSON() ([]byte, error) { return []byte(v.String()), nil }
 
 func (a Decimal) Scaled() int64 { return a.v }
 
-func (a Decimal) Float32() float32 { return float32(a.v) / float32(multipliers[FractionDigits]) }
+func (a Decimal) Float32() float32 { return float32(a.v) / float32(multiplier) }
 
-func (a Decimal) Float64() float64 { return float64(a.v) / float64(multipliers[FractionDigits]) }
+func (a Decimal) Float64() float64 { return float64(a.v) / float64(multiplier) }
 
-func (a Decimal) String() string { return FixedPointDecimalToString(a.v, FractionDigits) }
+func (a Decimal) String() string { return fpdecimal.FixedPointDecimalToString(a.v, fractionDigits) }
 
 func (a Decimal) Add(b Decimal) Decimal { return Decimal{v: a.v + b.v} }
 
 func (a Decimal) Sub(b Decimal) Decimal { return Decimal{v: a.v - b.v} }
 
-func (a Decimal) Mul(b Decimal) Decimal { return Decimal{v: a.v * b.v / multipliers[FractionDigits]} }
+func (a Decimal) Mul(b Decimal) Decimal { return Decimal{v: a.v * b.v / multiplier} }
 
-func (a Decimal) Div(b Decimal) Decimal { return Decimal{v: a.v * multipliers[FractionDigits] / b.v} }
+func (a Decimal) Div(b Decimal) Decimal { return Decimal{v: a.v * multiplier / b.v} }
 
-func (a Decimal) Mod(b Decimal) Decimal { return Decimal{v: a.v % (b.v / multipliers[FractionDigits])} }
+func (a Decimal) Mod(b Decimal) Decimal { return Decimal{v: a.v % (b.v / multiplier)} }
 
 func (a Decimal) DivMod(b Decimal) (part, remainder Decimal) { return a.Div(b), a.Mod(b) }
 

fpdecimal_test.go fp3/fpdecimal_test.gofpdecimal_test.go renamed to fp3/fpdecimal_test.go

@@ -1,4 +1,4 @@
-package fpdecimal_test
+package fp3_test
 
 import (
 	"encoding/json"
@@ -9,11 +9,9 @@ import (
 	"testing"
 	"unsafe"
 
-	fp "github.com/nikolaydubina/fpdecimal"
+	fp "github.com/nikolaydubina/fpdecimal/fp3"
 )
 
-var multipliers = [...]int64{1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000, 10000000000}
-
 func FuzzArithmetics(f *testing.F) {
 	tests := [][2]int64{
 		{1, 2},
@@ -108,6 +106,11 @@ func FuzzParse_StringSameAsFloat(f *testing.F) {
 			t.Skip()
 		}
 
+		// gaps start around these floats
+		if r > 100_000_000 || r < -100_000_000 {
+			t.Skip()
+		}
+
 		s := fmt.Sprintf("%.3f", r)
 		rs, _ := strconv.ParseFloat(s, 64)
 
@@ -176,12 +179,8 @@ func FuzzToFloat(f *testing.F) {
 	f.Fuzz(func(t *testing.T, v float64) {
 		a := fp.FromFloat(v)
 
-		if float32(v) != a.Float32() {
-			t.Error("a", a, "a.f32", a.Float32(), "f32.v", float32(v))
-		}
-
-		if v != a.Float64() {
-			t.Error("a", a, "a.f32", a.Float32(), "v", v)
+		if delta := math.Abs(v - a.Float64()); delta > 0.00100001 {
+			t.Error("a", a, "a.f64", a.Float64(), "v", v, "delta", delta)
 		}
 	})
 }
@@ -608,27 +607,3 @@ func TestDecimal_Compare(t *testing.T) {
 		t.Error(a, "==", b)
 	}
 }
-
-func TestSetFractionDigits(t *testing.T) {
-	defer func() { fp.FractionDigits = 3 }()
-
-	t.Run("default 3", func(t *testing.T) {
-		if a, err := fp.FromString("1.123"); a.String() != "1.123" || err != nil {
-			t.Error("SetFractionDigits", a)
-		}
-	})
-
-	t.Run("5", func(t *testing.T) {
-		fp.FractionDigits = 5
-		if a, err := fp.FromString("1.123456"); a.String() != "1.12345" || err != nil {
-			t.Error("SetFractionDigits 5", a)
-		}
-	})
-
-	t.Run("10", func(t *testing.T) {
-		fp.FractionDigits = 10
-		if a, err := fp.FromString("1.12345678910"); a.String() != "1.1234567891" || err != nil {
-			t.Error("SetFractionDigits 10", a)
-		}
-	})
-}

fp6/fpdecimal.go

@@ -0,0 +1,107 @@
+package fp6
+
+import "github.com/nikolaydubina/fpdecimal"
+
+// Decimal with 6 fractional digits.
+// Fractions lower than that are discarded in operations.
+// Max: +9223372036854.775807
+// Min: -9223372036854.775808
+type Decimal struct{ v int64 }
+
+var Zero = Decimal{}
+
+type integer interface {
+	int | int8 | int16 | int32 | int64 | uint | uint8 | uint16 | uint32 | uint64
+}
+
+const (
+	fractionDigits = 6
+	multiplier     = 1_000_000
+)
+
+func FromInt[T integer](v T) Decimal { return Decimal{int64(v) * multiplier} }
+
+func FromFloat[T float32 | float64](v T) Decimal {
+	return Decimal{int64(float64(v) * float64(multiplier))}
+}
+
+// FromIntScaled expects value already scaled to minor units
+func FromIntScaled[T integer](v T) Decimal { return Decimal{int64(v)} }
+
+func FromString(s string) (Decimal, error) {
+	v, err := fpdecimal.ParseFixedPointDecimal([]byte(s), fractionDigits)
+	return Decimal{v}, err
+}
+
+func (v *Decimal) UnmarshalJSON(b []byte) (err error) {
+	v.v, err = fpdecimal.ParseFixedPointDecimal(b, fractionDigits)
+	return err
+}
+
+func (v Decimal) MarshalJSON() ([]byte, error) { return []byte(v.String()), nil }
+
+func (a Decimal) Scaled() int64 { return a.v }
+
+func (a Decimal) Float32() float32 { return float32(a.v) / float32(multiplier) }
+
+func (a Decimal) Float64() float64 { return float64(a.v) / float64(multiplier) }
+
+func (a Decimal) String() string { return fpdecimal.FixedPointDecimalToString(a.v, fractionDigits) }
+
+func (a Decimal) Add(b Decimal) Decimal { return Decimal{v: a.v + b.v} }
+
+func (a Decimal) Sub(b Decimal) Decimal { return Decimal{v: a.v - b.v} }
+
+func (a Decimal) Mul(b Decimal) Decimal { return Decimal{v: a.v * b.v / multiplier} }
+
+func (a Decimal) Div(b Decimal) Decimal { return Decimal{v: a.v * multiplier / b.v} }
+
+func (a Decimal) Mod(b Decimal) Decimal { return Decimal{v: a.v % (b.v / multiplier)} }
+
+func (a Decimal) DivMod(b Decimal) (part, remainder Decimal) { return a.Div(b), a.Mod(b) }
+
+func (a Decimal) Equal(b Decimal) bool { return a.v == b.v }
+
+func (a Decimal) GreaterThan(b Decimal) bool { return a.v > b.v }
+
+func (a Decimal) LessThan(b Decimal) bool { return a.v < b.v }
+
+func (a Decimal) GreaterThanOrEqual(b Decimal) bool { return a.v >= b.v }
+
+func (a Decimal) LessThanOrEqual(b Decimal) bool { return a.v <= b.v }
+
+func (a Decimal) Compare(b Decimal) int {
+	if a.LessThan(b) {
+		return -1
+	}
+	if a.GreaterThan(b) {
+		return 1
+	}
+	return 0
+}
+
+func Min(vs ...Decimal) Decimal {
+	if len(vs) == 0 {
+		panic("min of empty set is undefined")
+	}
+	var v Decimal = vs[0]
+	for _, q := range vs {
+		if q.LessThan(v) {
+			v = q
+		}
+	}
+	return v
+}
+
+func Max(vs ...Decimal) Decimal {
+	if len(vs) == 0 {
+		panic("max of empty set is undefined")
+	}
+	var v Decimal = vs[0]
+	for _, q := range vs {
+		if q.GreaterThan(v) {
+			v = q
+		}
+	}
+	return v
+}