<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Instead of “UnsafeRandomSource”, I would call it “ReproducibleRandomSource”. I have also found that you often need to be able to “rewind” a reproducible random source for graphics applications:</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>protocol ReproducibleRandomSource : RandomSource {</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>init(seed: UInt64)</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func mark()->Int</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func returnToMark(_ mark:Int) //These could use something like an index instead of Int. My version just returns 1 the first time you call mark(), 2 the second time, etc...</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div class=""><br class=""></div><div class="">Also, I find that there are just a few primitive types I actually need from a random source:</div><div class=""><br class=""></div><div class="">• Double (full coverage of possible values)</div><div class="">• Double (in range of 0…1)</div><div class="">• UInt32</div><div class=""><br class=""></div><div class="">The following are also nice to have (built from the above), and commonly used:</div><div class=""><br class=""></div><div class=""><div class="">• Bool / CoinFlip</div></div><div class="">• Int (positive value)</div><div class="">• FixedWidthInteger (of various sizes. Full coverage of possible values)</div><div class="">• Character/String</div><div class="">• CGFloat</div><div class=""><br class=""></div><div class="">Any other type can be built from these building blocks. I have a RandomSourceCreatable protocol which allows exactly that. Once you have that, you can put a method on random source which allows you to create any conforming type:</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>extension RandomSource {</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func next<T:RandomSourceCreatable>(_ type: T.Type)->T</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div class=""><br class=""></div><div class="">This is extremely useful to create colors, offsets, etc…</div><div class=""><br class=""></div><div class="">One thing we need to definitely consider are constraints which people may want on the random value. For example, should an Int be positive? Should it be in a certain range? I have a “constraints” parameter on my RandomSourceCreatable protocol to handle this, and it works well, but I am not 100% happy with the ergonomics. I also have a variant with an “in range:” parameter that works for simple linear types like Ints and Floats. We could do something like:</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>extension RandomSource {</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func next<T:RandomRangeCreatable>(_ type: T.Type, in range: ClosedRange<T>) -> T </div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div class=""><br class=""></div><div class="">Finally, don’t underestimate the usefulness of coinFlip and func oneIn(_ number:UInt)->Bool. They let you quickly branch based on a random value:</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>if source.oneIn(100) { //This will be true roughly 1 in 100 times</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>//Do something occasionally </div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div class=""><br class=""></div><div class="">Thanks,</div><div class="">Jon</div><div class=""><br class=""></div><br class=""><div><blockquote type="cite" class=""><div class="">On Sep 25, 2017, at 9:57 PM, Alejandro Alonso via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" class="">
<title class=""></title>
<div class="">
<div name="messageBodySection" style="font-size: 14px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;" class="">
Hello evolution,
<div class=""><br class="">
</div>
<div class="">I am very thankful for all the feedback, and I’ve been working on a design that tries to utilize everybody’s ideas. The link to what I have so far is here: <a href="https://gist.github.com/Azoy/15f0518df38df9b722d4cb17bafea4c1" class="">https://gist.github.com/Azoy/15f0518df38df9b722d4cb17bafea4c1</a>.
Please keep in mind this is just a design, no actual implementation as I would most likely need assistance in doing. The default source for randomness will use the OS’s unseeded CSPRNG. This current setup exposes developers to an API that lets them create
their own RandomSources on the fly. I want to make the distinction that any existing or new sources of randomness that conform to UnsafeRandomSource are to be considered non cryptographically secure.</div>
<div class=""><br class="">
</div>
<div class="">I would love to get this discussion flowing again, and I would love input on the design. A few things I came across with this design is that some may want to use ranges as an argument for the numeric types, RandomAccessCollection returning an optional
when getting a random, and how to incorporate an API that allows distributions. I wanted to get input on how you feel about each of these topics as I’m indifferent about them all. I’m in no way saying this is the design we should go for, but I’m simply providing
something I think we should build on or talk about.</div>
</div>
<div name="messageSignatureSection" style="font-size: 14px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;" class="">
<br class="">
- Alejandro</div>
<div name="messageReplySection" style="font-size: 14px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;" class="">
<br class="">
On Sep 8, 2017, 11:52 AM -0500, Alejandro Alonso via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>>, wrote:<br class="">
<blockquote type="cite" style="margin: 5px 5px; padding-left: 10px; border-left: thin solid #1abc9c;" class="">
<div name="messageBodySection" style="font-size: 14px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;" class="">
Hello swift evolution, I would like to propose a unified approach to `random()` in Swift. I have a simple implementation here <a href="https://gist.github.com/Azoy/5d294148c8b97d20b96ee64f434bb4f5" class="">https://gist.github.com/Azoy/5d294148c8b97d20b96ee64f434bb4f5</a>.
This implementation is a simple wrapper over existing random functions so existing code bases will not be affected. Also, this approach introduces a new random feature for Linux users that give them access to upper bounds, as well as a lower bound for both
Glibc and Darwin users. This change would be implemented within Foundation.
<div class=""><br class="">
</div>
<div class="">I believe this simple change could have a very positive impact on new developers learning Swift and experienced developers being able to write single random declarations.</div>
<div class=""><br class="">
</div>
<div class="">I’d like to hear about your ideas on this proposal, or any implementation changes if need be.</div>
<div class=""><br class="">
</div>
<div class="">- Alejando</div>
</div>
<div name="messageReplySection" style="font-size: 14px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;" class="">
<br class="">
<div class=""></div>
</div>
</blockquote>
</div>
</div>
_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class="">https://lists.swift.org/mailman/listinfo/swift-evolution<br class=""></div></blockquote></div><br class=""></body></html>