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[SR-15134] Decimal.init(sign:exponent:significand:) gives incorrect values when exponent overflow or underflows #3360

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xwu opened this issue Aug 29, 2021 · 1 comment
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[SR-15134] Decimal.init(sign:exponent:significand:) gives incorrect values when exponent overflow or underflows #3360

xwu opened this issue Aug 29, 2021 · 1 comment
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xwu commented Aug 29, 2021

Previous ID SR-15134
Radar None
Original Reporter @xwu
Type Bug
Status Resolved
Resolution Done
Additional Detail from JIRA
Votes 0
Component/s Foundation
Labels Bug
Assignee @xwu
Priority Medium

md5: 90fff27aa26c010ed376b88af6f68045

relates to:

  • SR-15132 Decimal.significand gives wrong sign for negative values

Issue Description:

Consider the following behavior of Double:

let x = Double.leastNonzeroMagnitude
print(Double(sign: .plus, exponent: -10, significand: x)) // 0.0
let y = Double.greatestFiniteMagnitude
print(Double(sign: .plus, exponent: 10, significand: y)) // inf

Unfortunately, Decimal does not consider what happens when exponents are incremented out of range, and the result is dramatically wrong:

import Foundation
let a = Decimal.leastNonzeroMagnitude
print(Decimal(sign: .plus, exponent: -10, significand: a))
// 100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
let b = Decimal.greatestFiniteMagnitude
print(Decimal(sign: .plus, exponent: 10, significand: b))
// 0.00000000000000000000000000000000000000000000000000000000000000000000000000000000340282366920938463463374607431768211455
@xwu
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xwu commented Aug 31, 2021

#3068

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@shahmishal shahmishal transferred this issue from apple/swift May 5, 2022
This issue was closed.
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