Another option that I've been using a bit recently is:
(->> [(if some-condition? some-thing)
(if some-other-condition? some-other-thing)
...]
(filterv (complement nil?)))
Which when the list of expressions is long (more than 3-4 or so) is the
most readable alternative I've come up with.
Cheers,
Colin
On 22 May 2014 09:50, Colin Yates <colin.ya...@gmail.com> wrote:
> Thanks Herwig, cond-> looks just the ticket.
>
> Off the read the core API again :).
>
> On Wednesday, 21 May 2014 17:49:11 UTC+1, Herwig Hochleitner wrote:
>
>> I like to build more complex sequences within the sequence monad, like
>> this:
>>
>> (concat
>> (when cond1 [start elements])
>> main-seq
>> (when cond2 [end elements]))
>>
>> This also composes nicely with function calls.
>>
>> Another option for a subset of cases:
>>
>> (cond-> start-vec
>> condition1 (conj end-element1)
>> condition2 (conj end-element2))
>>
>> kind regards
>>
>>
>> 2014-05-21 18:23 GMT+02:00 Colin Yates <colin...@gmail.com>:
>>
>>> I often find myself doing the following:
>>>
>>> (let [some-seq []
>>> some_seq (if some-condition? (conj some-seq some-element) some-seq)
>>> some_seq (if some-other-condition? (conj some-seq
>>> some-other-element) some-seq)
>>> some_seq etc.])
>>>
>>> In other words building up a sequence which contains the results of
>>> predicated elements. Building up a where clause in SQL for example.
>>>
>>> I experimented with the -> and ->> but that didn't help and just looked
>>> messier.
>>>
>>> How do you handle this pretty common use case?
>>>
>>> Thanks!
>>>
>>>
>>>
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