Merge aa070c4ec8 into a1bdfc355e

CHANGELOG.md

@@ -1,3 +1,30 @@
+## Decimal v1.4.0
+#### BREAKING
+- Drop support for Go version older than 1.10 [#361](https://github.com/shopspring/decimal/pull/361)
+
+#### FEATURES
+- Add implementation of natural logarithm [#339](https://github.com/shopspring/decimal/pull/339) [#357](https://github.com/shopspring/decimal/pull/357)
+- Add improved implementation of power operation [#358](https://github.com/shopspring/decimal/pull/358)
+- Add Compare method which forwards calls to Cmp [#346](https://github.com/shopspring/decimal/pull/346)
+- Add NewFromBigRat constructor [#288](https://github.com/shopspring/decimal/pull/288)
+- Add NewFromUint64 constructor [#352](https://github.com/shopspring/decimal/pull/352)
+
+#### ENHANCEMENTS
+- Migrate to Github Actions [#245](https://github.com/shopspring/decimal/pull/245) [#340](https://github.com/shopspring/decimal/pull/340)
+- Fix examples for RoundDown, RoundFloor, RoundUp, and RoundCeil [#285](https://github.com/shopspring/decimal/pull/285) [#328](https://github.com/shopspring/decimal/pull/328) [#341](https://github.com/shopspring/decimal/pull/341)
+- Use Godoc standard to mark deprecated Equals and StringScaled methods [#342](https://github.com/shopspring/decimal/pull/342)
+- Removed unnecessary min function for RescalePair method [#265](https://github.com/shopspring/decimal/pull/265)
+- Avoid reallocation of initial slice in MarshalBinary (GobEncode) [#355](https://github.com/shopspring/decimal/pull/355)
+- Optimize NumDigits method [#301](https://github.com/shopspring/decimal/pull/301) [#356](https://github.com/shopspring/decimal/pull/356)
+- Optimize BigInt method [#359](https://github.com/shopspring/decimal/pull/359)
+- Support scanning uint64 [#131](https://github.com/shopspring/decimal/pull/131) [#364](https://github.com/shopspring/decimal/pull/364)
+- Add docs section with alternative libraries [#363](https://github.com/shopspring/decimal/pull/363)
+
+#### BUGFIXES
+- Fix incorrect calculation of decimal modulo [#258](https://github.com/shopspring/decimal/pull/258) [#317](https://github.com/shopspring/decimal/pull/317)
+- Allocate new(big.Int) in Copy method to deeply clone it [#278](https://github.com/shopspring/decimal/pull/278)
+- Fix overflow edge case in QuoRem method [#322](https://github.com/shopspring/decimal/pull/322)
+
 ## Decimal v1.3.1
 
 #### ENHANCEMENTS

README.md

@@ -24,6 +24,11 @@ Run `go get github.com/shopspring/decimal`
 
 Decimal library requires Go version `>=1.10`
 
+## Documentation
+
+http://godoc.org/github.com/shopspring/decimal
+
+
 ## Usage
 
 ```go
@@ -59,9 +64,16 @@ func main() {
 }
 ```
 
-## Documentation
+## Alternative libraries
 
-http://godoc.org/github.com/shopspring/decimal
+When working with decimal numbers, you might face problems this library is not perfectly suited for. 
+Fortunately, thanks to the wonderful community we have a dozen other libraries that you can choose from.  
+Explore other alternatives to find the one that best fits your needs :)  
+
+* [cockroachdb/apd](https://github.com/cockroachdb/apd) - arbitrary precision, mutable and rich API similar to `big.Int`, more performant than this library 
+* [alpacahq/alpacadecimal](https://github.com/alpacahq/alpacadecimal) - high performance, low precision (12 digits), fully compatible API with this library 
+* [govalues/decimal](https://github.com/govalues/decimal) - high performance, zero-allocation, low precision (19 digits)
+* [greatcloak/decimal](https://github.com/greatcloak/decimal) - fork focusing on billing and e-commerce web application related use cases, includes out-of-the-box BSON marshaling support
 
 ## FAQ
 

decimal.go

@@ -19,6 +19,7 @@ package decimal
 import (
 	"database/sql/driver"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"math"
 	"math/big"
@@ -1847,6 +1848,11 @@ func (d *Decimal) Scan(value interface{}) error {
 		*d = New(v, 0)
 		return nil
 
+	case uint64:
+		// while clickhouse may send 0 in db as uint64
+		*d = NewFromUint64(v)
+		return nil
+
 	default:
 		// default is trying to interpret value stored as string
 		str, err := unquoteIfQuoted(v)
@@ -2332,3 +2338,59 @@ func (d Decimal) Tan() Decimal {
 	}
 	return y
 }
+
+// More math
+
+// Sqrt returns the square root of d, accurate to DivisionPrecision decimal places.
+// Sqrt is only valid for non-negative numbers; it will return an error otherwise.
+func (d Decimal) Sqrt() (Decimal, error) {
+	s, _, err := d.SqrtRound(int32(DivisionPrecision))
+	return s, err
+}
+
+// ErrImaginaryResult indicates an operation that would produce an imaginary result.
+var ErrImaginaryResult = errors.New("The result of this operation is imaginary.")
+
+// SqrtMaxIter sets a limit for number of iterations for the Sqrt function
+const SqrtMaxIter = 1000000
+
+// SqrtRound returns the square root of d, accurate to precision decimal places.
+// The bool precise returns whether the precision was achieved.
+// SqrtRound is only valid for non-negative numbers; it will return an error otherwise.
+func (d Decimal) SqrtRound(precision int32) (Decimal, bool, error) {
+	var (
+		maxError = New(1, -precision)
+		one      = NewFromFloat(1)
+		lo, hi   Decimal
+	)
+
+	// Handle cases where d < 0, d = 0, 0 < d < 1, and d > 1
+	if d.GreaterThanOrEqual(one) {
+		lo = Zero
+		hi = d
+	} else if d.Equal(one) {
+		return one, true, nil
+	} else if d.LessThan(Zero) {
+		return Zero, false, ErrImaginaryResult
+	} else if d.Equal(Zero) {
+		return Zero, true, nil
+	} else {
+		// d is between 0 and 1. Therefore, 0 < d < Sqrt(d) < 1.
+		lo = d
+		hi = one
+	}
+
+	var mid Decimal
+	for i := 0; i < SqrtMaxIter; i++ {
+		mid = lo.Add(hi).Div(New(2, 0)) //mid = (lo+hi)/2;
+		if mid.Mul(mid).Sub(d).Abs().LessThan(maxError) {
+			return mid, true, nil
+		}
+		if mid.Mul(mid).GreaterThan(d) {
+			hi = mid
+		} else {
+			lo = mid
+		}
+	}
+	return mid, false, nil
+}

decimal_test.go

@@ -2416,104 +2416,57 @@ func TestDecimal_Max(t *testing.T) {
 	}
 }
 
-func TestDecimal_Scan(t *testing.T) {
-	// test the Scan method that implements the
-	// sql.Scanner interface
-	// check for the for different type of values
-	// that are possible to be received from the database
-	// drivers
+func scanHelper(t *testing.T, dbval interface{}, expected Decimal) {
+	t.Helper()
 
-	// in normal operations the db driver (sqlite at least)
-	// will return an int64 if you specified a numeric format
 	a := Decimal{}
-	dbvalue := 54.33
-	expected := NewFromFloat(dbvalue)
-
-	err := a.Scan(dbvalue)
-	if err != nil {
+	if err := a.Scan(dbval); err != nil {
 		// Scan failed... no need to test result value
-		t.Errorf("a.Scan(54.33) failed with message: %s", err)
-
-	} else {
+		t.Errorf("a.Scan(%v) failed with message: %s", dbval, err)
+	} else if !a.Equal(expected) {
 		// Scan succeeded... test resulting values
-		if !a.Equal(expected) {
 		t.Errorf("%s does not equal to %s", a, expected)
 	}
 }
 
+func TestDecimal_Scan(t *testing.T) {
+	// test the Scan method that implements the sql.Scanner interface
+	// check different types received from various database drivers
+
+	dbvalue := 54.33
+	expected := NewFromFloat(dbvalue)
+	scanHelper(t, dbvalue, expected)
+
 	// apparently MySQL 5.7.16 and returns these as float32 so we need
 	// to handle these as well
 	dbvalueFloat32 := float32(54.33)
 	expected = NewFromFloat(float64(dbvalueFloat32))
-
-	err = a.Scan(dbvalueFloat32)
-	if err != nil {
-		// Scan failed... no need to test result value
-		t.Errorf("a.Scan(54.33) failed with message: %s", err)
-
-	} else {
-		// Scan succeeded... test resulting values
-		if !a.Equal(expected) {
-			t.Errorf("%s does not equal to %s", a, expected)
-		}
-	}
+	scanHelper(t, dbvalueFloat32, expected)
 
 	// at least SQLite returns an int64 when 0 is stored in the db
 	// and you specified a numeric format on the schema
 	dbvalueInt := int64(0)
 	expected = New(dbvalueInt, 0)
+	scanHelper(t, dbvalueInt, expected)
 
-	err = a.Scan(dbvalueInt)
-	if err != nil {
-		// Scan failed... no need to test result value
-		t.Errorf("a.Scan(0) failed with message: %s", err)
-
-	} else {
-		// Scan succeeded... test resulting values
-		if !a.Equal(expected) {
-			t.Errorf("%s does not equal to %s", a, expected)
-		}
-	}
+	// also test uint64
+	dbvalueUint64 := uint64(2)
+	expected = New(2, 0)
+	scanHelper(t, dbvalueUint64, expected)
 
 	// in case you specified a varchar in your SQL schema,
-	// the database driver will return byte slice []byte
+	// the database driver may return either []byte or string
 	valueStr := "535.666"
 	dbvalueStr := []byte(valueStr)
-	expected, err = NewFromString(valueStr)
+	expected, err := NewFromString(valueStr)
 	if err != nil {
 		t.Fatal(err)
 	}
-
-	err = a.Scan(dbvalueStr)
-	if err != nil {
-		// Scan failed... no need to test result value
-		t.Errorf("a.Scan('535.666') failed with message: %s", err)
-
-	} else {
-		// Scan succeeded... test resulting values
-		if !a.Equal(expected) {
-			t.Errorf("%s does not equal to %s", a, expected)
-		}
-	}
-
-	// lib/pq can also return strings
-	expected, err = NewFromString(valueStr)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	err = a.Scan(valueStr)
-	if err != nil {
-		// Scan failed... no need to test result value
-		t.Errorf("a.Scan('535.666') failed with message: %s", err)
-	} else {
-		// Scan succeeded... test resulting values
-		if !a.Equal(expected) {
-			t.Errorf("%s does not equal to %s", a, expected)
-		}
-	}
+	scanHelper(t, dbvalueStr, expected)
+	scanHelper(t, valueStr, expected)
 
 	type foo struct{}
+	a := Decimal{}
 	err = a.Scan(foo{})
 	if err == nil {
 		t.Errorf("a.Scan(Foo{}) should have thrown an error but did not")
@@ -3481,6 +3434,40 @@ func TestAvg(t *testing.T) {
 	}
 }
 
+func TestSqrtRound(t *testing.T) {
+	i := NewFromFloat(-1)
+	if _, err := i.Sqrt(); err != ErrImaginaryResult {
+		t.Errorf("Square root of -1 should produce error")
+	}
+
+	var vals = map[string]string{
+		// value : Sqrt(value)
+		"0.0":       "0.0",
+		"0.002342":  "0.0483942145302514",
+		"1.0":       "1.0",
+		"3.0":       "1.7320508075688773",
+		"4.0":       "2.0",
+		"4.5":       "2.1213203435596426",
+		"3289854.0": "1813.7954680724064485",
+	}
+
+	for val, expected := range vals {
+		v, err := NewFromString(val)
+		if err != nil {
+			t.Errorf("error parsing test value into Decimal")
+		}
+
+		e, err := NewFromString(expected)
+		if err != nil {
+			t.Errorf("error parsing test expected value into Decimal")
+		}
+
+		if sqrt, err := v.Sqrt(); err != nil || !sqrt.Equal(e) {
+			t.Errorf("Square root of %s should be %s, not %s (error: %s)", v, e, sqrt, err)
+		}
+	}
+}
+
 func TestRoundBankAnomaly(t *testing.T) {
 	a := New(25, -1)
 	b := New(250, -2)