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replaced original Div, added initialization check and and check for 0 in divide

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This commit is contained in:
Roland Averkamp 2015-09-03 17:24:49 +02:00
parent 87964935d0
commit 8b186db779
1 changed files with 10 additions and 12 deletions
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22
decimal.go
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@ -273,18 +273,7 @@ func (d Decimal) Mul(d2 Decimal) Decimal {
// Div returns d / d2. If it doesn't divide exactly, the result will have // Div returns d / d2. If it doesn't divide exactly, the result will have
// DivisionPrecision digits after the decimal point. // DivisionPrecision digits after the decimal point.
func (d Decimal) Div(d2 Decimal) Decimal { func (d Decimal) Div(d2 Decimal) Decimal {
// NOTE(vadim): division is hard, use Rat to do it return d.DivRound(d2,int32(DivisionPrecision))
ratNum := d.Rat()
ratDenom := d2.Rat()
quoRat := big.NewRat(0, 1).Quo(ratNum, ratDenom)
// HACK(vadim): converting from Rat to Decimal inefficiently for now
ret, err := NewFromString(quoRat.FloatString(DivisionPrecision))
if err != nil {
panic(err) // this should never happen
}
return ret
} }
// QuoRem does divsion with remainder // QuoRem does divsion with remainder
@ -294,8 +283,16 @@ func (d Decimal) Div(d2 Decimal) Decimal {
// 0 >= r > -abs(d2) * 10 ^(-precision) if d<0 // 0 >= r > -abs(d2) * 10 ^(-precision) if d<0
// Note that precision<0 is allowed as input. // Note that precision<0 is allowed as input.
func (d Decimal) QuoRem(d2 Decimal, precision int32) (Decimal, Decimal) { func (d Decimal) QuoRem(d2 Decimal, precision int32) (Decimal, Decimal) {
d.ensureInitialized()
d2.ensureInitialized()
if (d2.value.Sign()==0) {
panic("decimal division by 0")
}
scale := -precision scale := -precision
e := int64(d.exp - d2.exp - scale) e := int64(d.exp - d2.exp - scale)
if e > math.MaxInt32 || e < math.MinInt32 {
panic("overflow in decimal QuoRem")
}
var aa, bb, expo big.Int var aa, bb, expo big.Int
var scalerest int32 var scalerest int32
// d = a 10^ea // d = a 10^ea
@ -330,6 +327,7 @@ func (d Decimal) QuoRem(d2 Decimal, precision int32) (Decimal, Decimal) {
// if the quotient is negative then digit 5 is rounded down, away from 0 // if the quotient is negative then digit 5 is rounded down, away from 0
// Note that precision<0 is allowed as input. // Note that precision<0 is allowed as input.
func (d Decimal) DivRound(d2 Decimal, precision int32) Decimal { func (d Decimal) DivRound(d2 Decimal, precision int32) Decimal {
// QuoRem already checks initialization
q, r := d.QuoRem(d2, precision) q, r := d.QuoRem(d2, precision)
// the actual rounding decision is based on comparing r*10^precision and d2/2 // the actual rounding decision is based on comparing r*10^precision and d2/2
// instead compare 2 r 10 ^precision and d2 // instead compare 2 r 10 ^precision and d2