On 13 Dec 2008, at 12:39, Dave Newton wrote:
>
> --- On Sat, 12/13/08, Stephen Parker wrote:
>> On 12 Dec 2008, at 23:10, Mark Fredrickson wrote:
>>> [...] insert 3 before every item less than or equal to 5 in a seq:
>>
>> (def bar [24 6 5 5 7 5 8 2])
>> (insert-before-if #(<= 5 %) 3 bar)
>>
>> =>
--- On Sat, 12/13/08, Stephen Parker wrote:
> On 12 Dec 2008, at 23:10, Mark Fredrickson wrote:
>> [...] insert 3 before every item less than or equal to 5 in a seq:
>
> (def bar [24 6 5 5 7 5 8 2])
> (insert-before-if #(<= 5 %) 3 bar)
>
> => (3 24 3 6 3 5 3 5 3 7 3 5 3 8 2)
Er...
Dave
--~--
On 12 Dec 2008, at 23:10, Mark Fredrickson wrote:
>> For (2), say I want to insert 3 before every item less than or equal
>> to 5 in a seq:
>
> Again reduce to the rescue:
>
> (reduce into (map (fn [i] (if (<= i 5) [3 i] [i])) [24 6 5 5 7 5 8
> 2]))
Could use mapcat:
(def bar [24 6 5 5 7 5 8
Thanks, Mark.
I don't suppose (reduce into ...) is a common enough idiom that it
deserves its own function? Perhaps (into x) should do (reduce into x),
e.g. (into [[3 5] [6 7]]) => [3 5 6 7]. This makes sense to me, but
maybe it's too semantically different from (into x y). If not, though,
you co
>
> For (1), it seems you generally resort to some kind of recursion with
> loop/recur. Say we wish to find the max value in a list (without using
> 'max'):
I can do this with reduce:
user=> (defn my-max [lst] (reduce (fn [x a] (if (> x a) x a)) (first
lst) (rest lst)))
#'user/my-max
user=> (my
A very large chunk of iteration is done for the sake of producing a
new collection based on an existing collection, hence functional
constructs like list comprehensions and map. However, I'm not sure
about how to functionally handle cases of iteration which seem to
require:
1) keeping around valu
