Add NewFromBigRat constructor (#288)

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Dovydas 2024-02-20 00:13:43 +02:00 committed by GitHub
parent 57a340d853
commit d00399e161
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2 changed files with 65 additions and 0 deletions

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@ -124,6 +124,26 @@ func NewFromBigInt(value *big.Int, exp int32) Decimal {
}
}
// NewFromBigRat returns a new Decimal from a big.Rat. The numerator and
// denominator are divided and rounded to the given precision.
//
// Example:
//
// d1 := NewFromBigRat(big.NewRat(0, 1), 0) // output: "0"
// d2 := NewFromBigRat(big.NewRat(4, 5), 1) // output: "0.8"
// d3 := NewFromBigRat(big.NewRat(1000, 3), 3) // output: "333.333"
// d4 := NewFromBigRat(big.NewRat(2, 7), 4) // output: "0.2857"
//
func NewFromBigRat(value *big.Rat, precision int32) Decimal {
return Decimal{
value: new(big.Int).Set(value.Num()),
exp: 0,
}.DivRound(Decimal{
value: new(big.Int).Set(value.Denom()),
exp: 0,
}, precision)
}
// NewFromString returns a new Decimal from a string representation.
// Trailing zeroes are not trimmed.
//

View file

@ -556,6 +556,51 @@ func TestNewFromBigIntWithExponent(t *testing.T) {
}
}
func TestNewFromBigRat(t *testing.T) {
mustParseRat := func(val string) *big.Rat {
num, _ := new(big.Rat).SetString(val)
return num
}
type Inp struct {
val *big.Rat
prec int32
}
tests := map[Inp]string{
Inp{big.NewRat(0, 1), 16}: "0",
Inp{big.NewRat(4, 5), 16}: "0.8",
Inp{big.NewRat(10, 2), 16}: "5",
Inp{big.NewRat(1023427554493, 43432632), 16}: "23563.5628642767953828", // rounded
Inp{big.NewRat(1, 434324545566634), 16}: "0.0000000000000023",
Inp{big.NewRat(1, 3), 16}: "0.3333333333333333",
Inp{big.NewRat(2, 3), 2}: "0.67", // rounded
Inp{big.NewRat(2, 3), 16}: "0.6666666666666667", // rounded
Inp{big.NewRat(10000, 3), 16}: "3333.3333333333333333",
Inp{mustParseRat("30702832066636633479"), 16}: "30702832066636633479",
Inp{mustParseRat("487028320159896636679.1827512895753"), 16}: "487028320159896636679.1827512895753",
Inp{mustParseRat("127028320612589896636633479.173582751289575278357832"), -2}: "127028320612589896636633500", // rounded
Inp{mustParseRat("127028320612589896636633479.173582751289575278357832"), 16}: "127028320612589896636633479.1735827512895753", // rounded
Inp{mustParseRat("127028320612589896636633479.173582751289575278357832"), 32}: "127028320612589896636633479.173582751289575278357832",
}
// add negatives
for p, s := range tests {
if p.val.Cmp(new(big.Rat)) > 0 {
tests[Inp{p.val.Neg(p.val), p.prec}] = "-" + s
}
}
for input, s := range tests {
d := NewFromBigRat(input.val, input.prec)
if d.String() != s {
t.Errorf("expected %s, got %s (%s, %d)",
s, d.String(),
d.value.String(), d.exp)
}
}
}
func TestCopy(t *testing.T) {
origin := New(1, 0)
cpy := origin.Copy()