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From Schalk Cronjé <ysb...@gmail.com>
Subject Re: Iterate over 2 lists in a closure?
Date Fri, 02 Oct 2015 14:50:13 GMT
I like the zip_longest suggestion.

On 02/10/2015 14:08, Winnebeck, Jason wrote:
> As for Dinko's note that transpose is on List -- I don't know how I've missed it -- I
had been looking for this feature in Groovy a long time (under the name of "zip" like it's
found in Python). Maybe it's because I normally check Iterable and Collection added methods
more often than list. I would second Schalk's comment about adding a zip function that works
with Iterable/Iterator. Whether or not it should match with "null" when one iterator is longer
than the other is up for debate, but both transpose in Groovy and zip in Python both ignore
any "extra" elements, although there is a zip_longest() in Python that takes a "fill value"
to use. I'd propose the method is defined so any of the following work:
>
> zip(a, b)
> a.zip(b)
> zip(a, b,c,d)
> a.zip(b,c,d)
>
> I think that would be compatible with Groovy extension methods if it's defined as:
>
> static <T> Iterable<T> zip(Iterable<? extends T> self, Iterable<?
extends T>... others)
>
> Jason
>
> -----Original Message-----
> From: Schalk Cronjé [mailto:ysb33r@gmail.com]
> Sent: Friday, October 02, 2015 5:22 AM
> To: users@groovy.incubator.apache.org
> Subject: Re: Iterate over 2 lists in a closure?
>
> This thread made me think a zip iterator could be a useful addition to the language.
>
>     def myList = [1,2,3]
>     def myMap = [ a:'b', c:'d', e:'f' ]
>     zip(myList,myMap).each { l,m -> println "$l $m" }
>
> Prints out
>     1 a=b
>     2 c=d
>     3 e=f
>
> If one collection is exhausted, whilst the other is not, then just return 'null' for
the additional items.
>
>
> On 02/10/2015 09:44, Dinko Srkoč wrote:
>> On 1 October 2015 at 19:47, Winnebeck, Jason
>> <Jason.Winnebeck@windstream.com> wrote:
>>> [...]
>>> This also sounds like a zip operation, which took me a really long time to
>>> find in Groovy but I recently found it:
>>>
>>>
>>>
>>> def letters = ['a', 'b']
>>> def numbers = [1, 2]
>>>
>>> assert ['a1', 'b2'] ==
>>>          GroovyCollections.transpose(letters, numbers).collect { it[0] + it[1]
>>> }
>>>
>> There's an easier way to use `transpose`:
>>
>>     assert ['a1', 'b2'] == [letters, numbers].transpose()*.join('')
>>
>> Cheers,
>> Dinko
>>
>>> In your case of testing a condition (equality) you can use any method
>>> instead of collect.
>>>
>>>
>>>
>>> Jason
>>>
>>>
>>>
>>> From: Owen Rubel [mailto:orubel@gmail.com]
>>> Sent: Thursday, October 01, 2015 1:28 PM
>>> To: users@groovy.incubator.apache.org
>>> Subject: Re: Iterate over 2 lists in a closure?
>>>
>>>
>>>
>>> if(list1.contains(list2) && list2.contains(list1)){ true }
>>>
>>>
>>> Owen Rubel
>>> 415-971-0976
>>> orubel@gmail.com
>>>
>>>
>>>
>>> On Thu, Oct 1, 2015 at 10:22 AM, Les Hartzman <lhartzman@gmail.com> wrote:
>>>
>>> Hi,
>>>
>>>
>>>
>>> I want to know if it's possible to have a closure that can iterate over 2
>>> equal length lists? The equivalent of doing list1.each, list2.each { ... },
>>> where each list is a list of an user-defined type.
>>>
>>>
>>>
>>> Basically I want to compare elements in the lists to see if they are equal.
>>>
>>>
>>>
>>> Thanks.
>>>
>>>
>>>
>>> Les
>>>
>>>
>>>
>>>
>>>
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>


-- 
Schalk W. Cronjé
Twitter / Ello / Toeter : @ysb33r


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