[squeak-dev] Re: Want: #slice: (Re: Noob question: array slice?)
Bert Freudenberg
bert at freudenbergs.de
Sat Aug 7 10:29:46 UTC 2010
On 07.08.2010, at 05:56, Andreas Raab wrote:
> On 8/6/2010 6:20 PM, Igor Stasenko wrote:
>> On 6 August 2010 17:45, Randal L. Schwartz<merlyn at stonehenge.com> wrote:
>>>>>>>> "Casey" == Casey Ransberger<casey.obrien.r at gmail.com> writes:
>>>
>>> Casey> It's literally adding a method to make the cuneiform smalltalk
>>> Casey> crap accessible to new people, who are liable to search on terms
>>> Casey> like 'slice.'
>>>
>>> What you are asking for is something that would be useful for only
>>> those first few hours, and then be a maintenance clutter for the
>>> remaining years of programming.
>>>
>>> I vote "-1".
>>>
>> +1 to your -1.
>
> I vote -2 on your -1 which should leave us at +0 I think :-)=)
>
> No, seriously. I think there's actually a pretty good and generic interpretation of slice if you consider it to be an operation that can collect arbitrary sequences. For example:
>
> Collection>>slice: aCollection
> "Slice the receiver by aCollection, collecting all elements
> in the receiver that are keyed by aCollection."
>
> ^aCollection collect:[:each| self at: each] as: self species.
>
> With a polymorphic implementation this would allow some interesting uses that are quite difficult to implement otherwise, for example:
>
> dd := Dictionary newFromPairs: {
> 'firstName'. 'Joe'.
> 'lastName'. 'Sixpack'
> 'dob'. '01-01-2001'.
> 'zip'. '12345'
> }.
> dd slice: #(firstName lastName).
>
> This would return a dictionary with only firstName and lastName. And of course, when used with intervals it would behave identical to #copyFrom:to: just somewhat less efficient, but that's offset by, say, uses such as:
>
> "Slice out all the odd elements"
> aCollection slice: (1 to: aCollection size by: 2).
>
> Etc. So I think the argument for #slice: can be made and we should consider it as a more generic operation instead of just a slower version of #copyFrom:to:.
But we have that already. It's called #atAll: which is nicely consistent with the rest of the collection protocols. We just need to add a more generic version in Collection.
- Bert -
More information about the Squeak-dev
mailing list
|