On Nov 29, 2008, at 6:49 AM, Daniel Renfer wrote:
> Even if you don't think you'll run into the possibility of blowing
> your stack, it's still a good idea to use recur when doing tail call
> recursion. The compiler will help you out by making sure it really is
> a tail call.
>
> Remember, recur isn't just for loop. It works with functions too.
In case that isn't clear, it means that anywhere you would do a self
call in a tail position you can replace it with recur to ensure no
stack growth, e.g. the first example could have been written:
(defn construct-atom
"translates a number n into an set of letters of size n"
[construct length]
(if (< (count construct) length)
(recur (conj construct (char (+ (rand-int amino_acids) 65))) length)
construct))
recur will goto the nearest enclosing loop or fn.
Rich
>
>
> On Sat, Nov 29, 2008 at 6:42 AM, bOR_ <[EMAIL PROTECTED]> wrote:
>>
>> In this case, the depth of the recursion would be at maximum 21
>> (number of different types of amino acids), and the function itself
>> not often called. Is stack size something to worry about at those
>> depths?
>>
>> On Nov 29, 11:11 am, "Kevin Downey" <[EMAIL PROTECTED]> wrote:
>>> the jvm does not do TCO, loop/recur allows for functional looking
>>> recursion on the jvm with constant stack size.
>>>
>>>
>>>
>>> On Sat, Nov 29, 2008 at 1:25 AM, bOR_ <[EMAIL PROTECTED]>
>>> wrote:
>>>
>>>> Hi all,
>>>
>>>> I wondered if there is a difference between using loop-recur or
>>>> merely
>>>> writing a recursive function. The main difference I found thus
>>>> far was
>>>> that the loop-recur can suffice with less arguments, but the
>>>> recursive
>>>> functions seem to be shorter, and perhaps more elegant?
>>>
>>>> (defn construct-atom
>>>> "translates a number n into an set of letters of size n"
>>>> [construct length]
>>>> (if (< (count construct) length)
>>>> (construct-atom (conj construct (char (+ (rand-int amino_acids)
>>>> 65))) length)
>>>> construct))
>>>
>>>> (defn construct-atom-loop
>>>> "translates a number n into an set of letters of size n"
>>>> [n]
>>>> (let [base_construct #{}]
>>>> (loop [construct base_construct]
>>>> (if (< (count construct) n)
>>>> (recur (conj construct (char (+ (rand-int amino_acids) 65))))
>>>> construct))))
>>>
>>> --
>>> And what is good, Phaedrus,
>>> And what is not good—
>>> Need we ask anyone to tell us these things?
>>>
>>
>
> >
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