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Respect rounding mode when quantizing sub-ULP values #152

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Respect rounding mode when quantizing sub-ULP values #152

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6 changes: 6 additions & 0 deletions context.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1182,7 +1182,13 @@ func (c *Context) quantize(d, v *Decimal, exp int32) Condition {
p := int32(d.NumDigits()) - diff
if p < 0 {
if !d.IsZero() {
var discard Decimal
discard.Coeff.Set(&d.Coeff)
discard.Exponent = -diff
d.Coeff.SetInt64(0)
if c.Rounding.ShouldAddOne(&d.Coeff, d.Negative, discard.Cmp(decimalHalf)) {
d.Coeff.SetInt64(1)
}
res = Inexact | Rounded
}
} else {
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35 changes: 35 additions & 0 deletions decimal_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -702,6 +702,41 @@ func TestQuantize(t *testing.T) {
}
}

func TestQuantizeRounding(t *testing.T) {
tests := []struct {
s string
e int32
rnd Rounder
expect string
}{
{s: "0.002", e: -1, rnd: RoundCeiling, expect: "0.1"},
{s: "1.002", e: -1, rnd: RoundCeiling, expect: "1.1"},
{s: "-0.002", e: -1, rnd: RoundCeiling, expect: "-0.0"},
{s: "0.002", e: -1, rnd: RoundFloor, expect: "0.0"},
{s: "-0.002", e: -1, rnd: RoundFloor, expect: "-0.1"},
{s: "0.002", e: -1, rnd: RoundUp, expect: "0.1"},
{s: "0.002", e: -1, rnd: RoundDown, expect: "0.0"},
{s: "0.04", e: -1, rnd: RoundHalfUp, expect: "0.0"},
{s: "0.05", e: -1, rnd: RoundHalfUp, expect: "0.1"},
{s: "0.05", e: -1, rnd: RoundHalfEven, expect: "0.0"},
}
for _, tc := range tests {
t.Run(fmt.Sprintf("%s: %d %s", tc.s, tc.e, tc.rnd), func(t *testing.T) {
c := Context{Precision: 100, Rounding: tc.rnd, MaxExponent: 1000, MinExponent: -1000, Traps: DefaultTraps}
d, _, err := NewFromString(tc.s)
if err != nil {
t.Fatal(err)
}
if _, err := c.Quantize(d, d, tc.e); err != nil {
t.Fatal(err)
}
if s := d.String(); s != tc.expect {
t.Fatalf("expected: %s, got: %s", tc.expect, s)
}
})
}
}

func TestCmpOrder(t *testing.T) {
tests := []struct {
s string
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