Implement except on Seq, Array and List by PatrickMcDonald · Pull Request #253 · dotnet/fsharp

PatrickMcDonald · 2015-02-20T09:49:23Z

This PR addresses Add 'except' function to core collection modules

The implementation suggested in uservoice is different from the LINQ implementation as LINQ Except removes duplicates from the results. I have gone with the LINQ version for the moment

forki · 2015-02-20T09:50:32Z

src/fsharp/FSharp.Core/seq.fsi

It's not exactly a set difference, right?

Maybe not, what's the 'difference' (oooh pun)

I just cogged the LINQ documentation

Ok. Then we should keep it that way. It's just a bit strange to talk about sets when we're actually in Streams or lists...

I think 'difference' does not necessarily imply that the result is unique elements, whereas 'set difference' [might|does]?

I thinks it#s exactly the point of https://github.com/Microsoft/visualfsharp/pull/253/files#r25061210

PatrickMcDonald · 2015-02-20T09:58:21Z

I have done some performance testing (code is in this fork)

Some results:

Iterations = 1000, n = 1000, m = 25, upper = 50

Enumerable.Except took 00:00:00.1324282
Seq.except took 00:00:00.1288203
Array.Except took 00:00:00.1381398
Seq.Except (on arrays) took 00:00:00.1309900
Enumerable.Except (on arrays) took 00:00:00.1191383
List.Except took 00:00:00.1321431
Seq.Except (on lists) took 00:00:00.1314925
Enumerable.Except (on lists) took 00:00:00.1203745

Iterations = 1000, n = 1000, m = 25, upper = 100000

Enumerable.Except took 00:00:00.1707046
Seq.except took 00:00:00.2006956
Array.Except took 00:00:00.1872810
Seq.Except (on arrays) took 00:00:00.1841139
Enumerable.Except (on arrays) took 00:00:00.1810613
List.Except took 00:00:00.1813101
Seq.Except (on lists) took 00:00:00.2028662
Enumerable.Except (on lists) took 00:00:00.1681396

forki · 2015-02-20T10:04:15Z

src/fsharp/FSharp.Core/array.fs

Can we rename the args to make it super obvious which one is which?

I went with array1/array2 as that is what is used elsewhere in the module, I agree it could be more meaningful, am open to suggestions here.

first/second is meaningless as well. I think that should be improved.

ignoredItems? itemsToRemove? excludedItems?

rojepp · 2015-02-20T11:54:51Z

Could you flip the argument order? I'd like to do [1;2;3;4] |> List.except [1;2].

forki · 2015-02-20T11:58:47Z

yep that's basically why I asked: #253 (comment)

dsyme · 2015-02-20T17:23:25Z

Yes, I would recommend that the arguments be flipped to allow pipelining - at least, that was my intention in suggesting that we look at implementing this. It's one reason why I prefer the name "except" to the name "difference".

latkin · 2015-02-20T21:40:43Z

src/fsharp/FSharp.Core.Unittests/SurfaceArea.net40.fs

Don't forget to update SurfaceArea.portable*.fs too

Change itemsToExclude from M(T) to seq<T>

latkin · 2015-02-24T19:54:21Z

LGTM

lasandell · 2015-03-28T14:01:52Z

I guess someone can close the related uservoice issue now. 👍

forki reviewed Feb 20, 2015
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PatrickMcDonald mentioned this pull request Feb 20, 2015

[Design] Implement except on seq, array and list fsharp/fslang-design#41

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Implement except on Seq, Array and List

646db39

PatrickMcDonald force-pushed the except branch from 5198763 to 646db39 Compare February 20, 2015 14:47

latkin reviewed Feb 20, 2015
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src/fsharp/FSharp.Core.Unittests/SurfaceArea.net40.fs Outdated

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Don't forget to update SurfaceArea.portable*.fs too

PatrickMcDonald added 2 commits February 21, 2015 15:30

Rename and reorder extract input parameters

a870b96

Change itemsToExclude from M(T) to seq<T>

Update portable surface area tests

8605516

latkin added the Feature Request label Feb 23, 2015

latkin closed this in 0676493 Feb 24, 2015

latkin added the fixed label Feb 24, 2015

PatrickMcDonald deleted the except branch February 25, 2015 13:53

mexx mentioned this pull request Mar 26, 2015

Add except on Seq, Array and List mexx/FSharp.Core.NextVersion.Shim#9

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cloudRoutine mentioned this pull request Oct 12, 2016

Add 'except' function to core collection modules cloudRoutine/issueTestRepo#405

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baronfel mentioned this pull request Oct 20, 2016

Add 'except' function to core collection modules fsharp/fslang-suggestions#405

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PatrickMcDonald commented Feb 20, 2015

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PatrickMcDonald commented Feb 20, 2015

Iterations = 1000, n = 1000, m = 25, upper = 50

Iterations = 1000, n = 1000, m = 25, upper = 100000

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rojepp commented Feb 20, 2015

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forki commented Feb 20, 2015

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latkin commented Feb 24, 2015

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