Clojure

quot overflow issues around Long/MIN_VALUE for BigInt

Details

  • Type: Defect Defect
  • Status: Open Open
  • Priority: Minor Minor
  • Resolution: Unresolved
  • Affects Version/s: Release 1.5
  • Fix Version/s: None
  • Component/s: None
  • Labels:
  • Patch:
    Code and Test
  • Approval:
    Triaged

Description

In Clojure 1.5.1, see the following undesirable behavior regarding incorrect quot results for BigInts:

user=> (quot Long/MIN_VALUE -1N)
-9223372036854775808N
user=> (quot (bigint Long/MIN_VALUE) -1)
-9223372036854775808N

Similar issue to CLJ-1222. The root cause is that Java division of longs gives a numerically incorrect answer of Long.MIN_VALUE for (Long.MIN_VALUE / -1), because the numerically correct answer does not fit in a long. I believe this is the only pair of arguments for long division that gives a numerically incorrect answer, because division with a denominator having an absolute value of 2 or more gives a result closer to 0 than the numerator, and everything works fine for a denominator of 1 or -1, except this one case.

Related issues: CLJ-1222 for multiply, CLJ-1253 for / on longs, CLJ-1254 for quot on longs

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  • Created:
    Updated: