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66
decimal.go
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@ -1544,6 +1544,72 @@ func (d Decimal) Round(places int32) Decimal {
return ret
}
// RoundHalfUp rounds the decimal half towards +infinity.
//
// Example:
//
// NewFromFloat(545).RoundHalfUp(-2).String() // output: "500"
// NewFromFloat(500).RoundHalfUp(-2).String() // output: "500"
// NewFromFloat(1.1001).RoundHalfUp(2).String() // output: "1.10"
// NewFromFloat(-1.454).RoundHalfUp(1).String() // output: "-1.4"
// NewFromFloat(-1.464).RoundHalfUp(1).String() // output: "-1.5"
func (d Decimal) RoundHalfUp(places int32) Decimal {
if d.exp == -places {
return d
}
// truncate to places + 1
ret := d.rescale(-places - 1)
// add sign(d) * 0.5
if ret.value.Sign() < 0 {
ret.value.Sub(ret.value, fourInt)
} else {
ret.value.Add(ret.value, fiveInt)
}
// floor for positive numbers, ceil for negative numbers
_, m := ret.value.DivMod(ret.value, tenInt, new(big.Int))
ret.exp++
if ret.value.Sign() < 0 && m.Cmp(zeroInt) != 0 {
ret.value.Add(ret.value, oneInt)
}
return ret
}
// RoundHalfDown rounds the decimal half towards -infinity.
//
// Example:
//
// NewFromFloat(550).RoundHalfDown(-2).String() // output: "500"
// NewFromFloat(560).RoundHalfDown(-2).String() // output: "600"
// NewFromFloat(1.1001).RoundHalfDown(2).String() // output: "1.11"
// NewFromFloat(-1.454).RoundHalfDown(1).String() // output: "-1.5"
// NewFromFloat(-1.444).RoundHalfDown(1).String() // output: "-1.4"
func (d Decimal) RoundHalfDown(places int32) Decimal {
if d.exp == -places {
return d
}
// truncate to places + 1
ret := d.rescale(-places - 1)
// add sign(d) * 0.5
if ret.value.Sign() < 0 {
ret.value.Sub(ret.value, fiveInt)
} else {
ret.value.Add(ret.value, fourInt)
}
// floor for positive numbers, ceil for negative numbers
_, m := ret.value.DivMod(ret.value, tenInt, new(big.Int))
ret.exp++
if ret.value.Sign() < 0 && m.Cmp(zeroInt) != 0 {
ret.value.Add(ret.value, oneInt)
}
return ret
}
// RoundCeil rounds the decimal towards +infinity.
//
// Example:

106
decimal_test.go
View file

@ -3647,3 +3647,109 @@ func ExampleNewFromFloat() {
//0.123123123123123
//-10000000000000
}
func TestDecimal_RoundHalfUp(t *testing.T) {
tests := []struct {
name string
d Decimal
places int32
want Decimal
}{
{
name: "550",
d: NewFromInt(550),
places: -2,
want: NewFromInt(600),
},
{
name: "545",
d: NewFromInt(545),
places: -2,
want: NewFromInt(500),
},
{
name: "500",
d: NewFromInt(500),
places: -2,
want: NewFromInt(500),
},
{
name: "1.1001",
d: NewFromFloat(1.1001),
places: 2,
want: NewFromFloat(1.10),
},
{
name: "-1.454",
d: NewFromFloat(-1.454),
places: 1,
want: NewFromFloat(-1.4),
},
{
name: "-1.464",
d: NewFromFloat(-1.464),
places: 1,
want: NewFromFloat(-1.5),
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
if got := tt.d.RoundHalfUp(tt.places); !got.Equal(tt.want) {
t.Errorf("RoundHalfUp() = %v, want %v", got, tt.want)
}
})
}
}
func TestDecimal_RoundHalfDown(t *testing.T) {
tests := []struct {
name string
d Decimal
places int32
want Decimal
}{
{
name: "550",
d: NewFromInt(550),
places: -2,
want: NewFromInt(500),
},
{
name: "560",
d: NewFromInt(560),
places: -2,
want: NewFromInt(600),
},
{
name: "500",
d: NewFromInt(500),
places: -2,
want: NewFromInt(500),
},
{
name: "1.1001",
d: NewFromFloat(1.1001),
places: 2,
want: NewFromFloat(1.10),
},
{
name: "-1.454",
d: NewFromFloat(-1.454),
places: 1,
want: NewFromFloat(-1.5),
},
{
name: "-1.444",
d: NewFromFloat(-1.444),
places: 1,
want: NewFromFloat(-1.4),
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
if got := tt.d.RoundHalfDown(tt.places); !got.Equal(tt.want) {
t.Errorf("RoundHalfDown() = %v, want %v", got, tt.want)
}
})
}
}