I think that’s splitting hairs a bit. Even if you see the loop you don’t know
the cost unless you know the size of a slice. For instance, a lookup in a small
slice is actually cheaper than a small map - in memory and speed. So you need
to know more than “it’s a slice” to make a judgement.
> On Nov 5, 2019, at 5:58 PM, Tyler Compton <xavi...@gmail.com> wrote:
>
>
> I agree with you that an original writer of the code should be expected to
> know that a theoretical "contains" or "in" expression has O(n) properties.
> However, I've always thought of this from the perspective of someone looking
> at the code later and trying to identify performance issues. It's easy to
> identify a potentially very costly iteration through a slice if it's more
> verbose and always expressed the same way.
>
>> On Tue, Nov 5, 2019 at 2:44 PM Robert Engels <reng...@ix.netcom.com> wrote:
>> Is it though?
>>
>> You would have the same problem if you thought the size of mySlice was
>> always small, and it wasn't - range could be quite expensive (or not) - and
>> if that was not valid workable you should be using something other than a
>> slice.
>>
>> You need understanding of the types and cost of operations in any language,
>> and the naming (or something else) should make the types easily recognizable
>> (and understandable).
>>
>>
>> -----Original Message-----
>> From: Tyler Compton
>> Sent: Nov 5, 2019 3:57 PM
>> To: toddsu...@icloud.com
>> Cc: golang-nuts
>> Subject: Re: [go-nuts] Why doesn't Go include a contains method for things
>> like slices?
>>
>> Ian's answer addresses your question about the absence of a slice.Contains
>> method, but there have been discussions in the past about adding such a
>> feature to the language itself as well. You brought up the idea of a builtin
>> "contains" function, and I've seen others suggest adding something like
>> Python's "in" operator as well. To most of these proposals, the answer has
>> been "no" because of concerns about hiding a potentially very expensive
>> operation behind a builtin or operator. There's no doubt that:
>>
>> return myObj in mySlice
>>
>> ... is easier to miss than:
>>
>> for _, obj := range mySlice {
>> if obj == myObj {
>> return true
>> }
>> }
>> return false
>>
>>> On Tue, Nov 5, 2019 at 12:30 PM toddsurfs via golang-nuts
>>> <golang-nuts@googlegroups.com> wrote:
>>> Sorry if this question reveals my newness to Go. I tried searching the
>>> mailing list but I couldn't find anything in a quick search. It seems like
>>> many languages include the ability to check if an array, or slice contain a
>>> particular value. I understand that you could do this easily with a for
>>> loop or alternatively use a map instead. However, is there a reason why Go
>>> doesn't just have slice.Contains(interface{}) or maybe a builtin
>>> contains(mySlice, interface{}) ?
>>>
>>> I assume one reason might be because slices could potentially be really
>>> large? Or maybe the community feels that a simple for loop is so easy that
>>> it is not necessary? I would love to understand this more.
>>>
>>> Thank You!
>>> -Todd
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>>
>>
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