Paul King created GROOVY-9981:
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Summary: CLONE - println(-0.0f) does not comply with IEEE754
Key: GROOVY-9981
URL: https://issues.apache.org/jira/browse/GROOVY-9981
Project: Groovy
Issue Type: Bug
Components: Groovysh
Affects Versions: 2.5.7, 2.4.17, 2.5.13, 3.0.6
Environment: Linux
Reporter: Jubilee
Assignee: Paul King
Fix For: 4.0.0-alpha-3
IEEE754-2019 (which supersedes all previous floating point standards for
decimal or binary floating point) states that an implementation *shall* (that
means "is required to") preserve the sign on floating point numbers when it
converts numbers to an "external decimal character sequence" (that means
"prints them the way everyone does, unless you use special formatting
characters I guess"), singling out the two zeros and the two infinities in
particular for this treatment.
IEEE754-2019 does not say this for no reason. It's because conformant floating
point implementations can print the float out and then later read it back into
its original floating point bit-pattern. A close reading of IEEE754-1985
suggests this was always the intention, but this requirement was made
unambiguously explicit for signed zeros as early as IEEE854-1987.
On all the versions of Apache Groovy's REPL that I was able to trivially easily
test, println(-0.0f) does not output "-0.0", but outputs "0.0" instead. While
I am aware that printf is also available in Groovy and can allow one to select
formatting, this should probably be considered a bug, especially given that
println in Java (OpenJDK 14) outputs "-0.0" and so do Kotlin, Scala, and
Clojure with their relevant commands.
This bug suggests there are other errors relevant to IEEE754 compliance in
relevant formatting and parsing code, so it is a good idea to do a more
thorough audit as well.
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