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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">I’m also fine with this hex-floats thing<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">What’s the protocol? Should committee discussion take place by default on the proposal thread itself, with exceptional out-of-band private discussion on the mailing list? Or by-default private
on the mailing list?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Simon<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> ghc-steering-committee [mailto:ghc-steering-committee-bounces@haskell.org]
<b>On Behalf Of </b>Simon Marlow<br>
<b>Sent:</b> 28 February 2017 13:37<br>
<b>To:</b> Iavor Diatchki <iavor.diatchki@gmail.com><br>
<b>Cc:</b> ghc-steering-committee@haskell.org<br>
<b>Subject:</b> Re: [ghc-steering-committee] Proposal: Accept proposal 37, Hex Float literals<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:0cm">
No objections from me. Looks useful and not too costly in terms of extra complexity.<o:p></o:p></p>
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<o:p> </o:p></p>
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On 27 February 2017 at 21:34, Iavor Diatchki <<a href="mailto:iavor.diatchki@gmail.com" target="_blank">iavor.diatchki@gmail.com</a>> wrote:<o:p></o:p></p>
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Hello,<o:p></o:p></p>
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<o:p> </o:p></p>
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I was assigned to be the shepherd for the Hex Float proposal (<a href="https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%2Fpull%2F37&data=02%7C01%7Csimonpj%40microsoft.com%7Cc043b1b23db44809543c08d45fdedd63%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636238858192460021&sdata=ce2UQC76fEIyTWo4rEY0UWo9AKfzCINM7q9nWuDAsSQ%3D&reserved=0" target="_blank">https://github.com/ghc-proposals/ghc-proposals/pull/37</a>),
so I would like to propose that we accept it for implementation in GHC.<o:p></o:p></p>
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<o:p> </o:p></p>
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This is a small change, which can be summarized as follows:<o:p></o:p></p>
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- allow floating point numbers to be written using hex digits.<o:p></o:p></p>
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<o:p> </o:p></p>
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The format is exactly the same as decimal floating point numbers, except for:<o:p></o:p></p>
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- the literals start with 0x<o:p></o:p></p>
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- the digits are in hex<o:p></o:p></p>
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- the exponent symbol is `p` or `P`, instead of `e` or `E`<o:p></o:p></p>
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- the exponent is in base 2, rather than base 10<o:p></o:p></p>
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<o:p> </o:p></p>
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This notation has become popular among people working with floating point numbers, as the numbers you write can be represented exactly, which is not the case for base 10 numbers.<o:p></o:p></p>
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<o:p> </o:p></p>
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The following points were discussed:<o:p></o:p></p>
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- the exact format to use, compared to what's allowed by other languages: we decided to just follow Haskell's decimal float notation, for least surprise<o:p></o:p></p>
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- should overflow (which becomes `Inf`) result in a warning? We decided that this is an orthogonal issue, also relevant to decimal floating point and made a GHC ticket (#13232)<o:p></o:p></p>
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- there is an odd interaction between floating point (both decimal and hex) and -XNegativeLiterals, related to negative 0, see ticket #13211<o:p></o:p></p>
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- changing the Read instances for Float and Double to recognize hex floats could break some programs, although that does not seem all that likely<o:p></o:p></p>
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- there is a question of how many extra pretty printing functions to add to `Numeric`: the current thinking is that maybe just one `showHFloat` is sufficient; the alternative is to add 5, mirroring the `show[E,F,G]Float` functions for decimals.<o:p></o:p></p>
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<o:p> </o:p></p>
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I also had a stab at implementing the basic notation here: <a href="https://phabricator.haskell.org/D3066" target="_blank">https://phabricator.haskell.org/D3066</a><o:p></o:p></p>
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I haven't done the changes to the libraries yet.<o:p></o:p></p>
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<o:p> </o:p></p>
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Please let me know if you have any objections or suggestions on what might needs to be changed.<o:p></o:p></p>
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<o:p> </o:p></p>
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Cheers,<o:p></o:p></p>
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-Iavor<o:p></o:p></p>
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<o:p> </o:p></p>
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<o:p> </o:p></p>
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<o:p> </o:p></p>
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<o:p> </o:p></p>
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<br>
_______________________________________________<br>
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