Wikipedia:Reference desk/Archives/Computing/2018 August 27

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August 27

Resource for 'soft' float conversion between 'single' and 'extended' precision...?

Does anyone have a link to a document or (more likely) a repository than gives an outline of how to convert single precision (32bit) to Extended precision 80 bit floating point number? I know on ia32(80x86) This can be done with fp instructions, but I was looking for a platform irrelevant version ( The context if it helps is connection with translating function returns in 3D graphics.) Thanks. ShakespeareFan00 (talk) 14:34, 27 August 2018 (UTC)

This describes the 32-bit single-precision floating-point format. This interprets the fields of the 80-bit format in the Intel 8087 math coprocessor and processors based on the x86 design. DroneB (talk) 17:35, 29 August 2018 (UTC)

A question about licenses

Suppose there is an open source (Apache License) implementation of X in Java. There exist other implementations in different languages (say JavaScript and Python) in different licenses (Unlicensed, CC-BY-SA, MIT, etc.)

It just happened that I translated the Java implementation to JavaScript and heavily edited it, so that even its functionality is practically different.

Noting that my derivation would be the exact same regardless of what implementation I started with, do I still need to respect the Apache License? Or (for my project's purposes) can I re-license it to something like CC0?

(I'm not trying to rip off anybody. These legal stuff confuse me.)

--إلياس الجزائري^Elias 14:45, 27 August 2018 (UTC)

Like most questions about licenses, you should consult an attorney experienced in software licensing. The ultimate answer, if a dispute arises, will be determined by whomever can make a convincing case in a court or other settlement. Nimur (talk) 23:36, 27 August 2018 (UTC)

• Did you build a derivative of some original creative work? You can change it, you can even change the implementation language - but it will still be a derivative work.

If you had an original work under a licence which permitted these and didn't specifically forbid derivatives (i.e. not a CC-nd), then you can do, but you may need to comply with some restrictions. These may be either requirements (Apache has some of these) such as retaining attribution for the original and redistributing copies of the licence itself with any code. There may be prohibitions on doing some things (Apache is light on these). Some - notably Gnu licences - will have stringent requirements on you making source for any derivative versions freely available.

It's rare to find a restriction on derivatives for open source software (CC-nd does this, but CC- licences aren't a god fit for software). However it would be an issue for commercial non-free software. In such a case, clean-room development might be a requirement, where you not only don't base you new work on the old work, but you do this in such a way that you can legally demonstrate that you did this, and there is thus no legal impediment to your new product. It's very common to need to do this where a protocol is open sourced or free, but an existing implementation is commercial, yet accessible. A second developer might need to show that they used the protocol, but not any of the copyrighted and unlicensed other implementation. Andy Dingley (talk) 22:58, 29 August 2018 (UTC)