[Haskell-cafe] Suspected stupid Haskell Question

[Big_Ham]

you are indeed right Peter, that's what I was after, the frequency regardless
of elements.  It also doesn't matter if it  outputs them as tuples, or as a
separate list on their own because each value would belong to the first
occurance of that element if you seem what I mean, so you could still tell
what came from what.


Peter Verswyvelen wrote:
> 
> I'm a newbie here, so I'm not sure about my reply, but I think this is 
> not the answer to his question.
> 
> freq ["egg", "egg", "cheese"] indeed returns [2,1]
> 
> but
> 
> freq ["egg", "cheese", "egg"] returns [1,1,1]
> 
> BH just mentioned he needed the frequenty of elements in the list, 
> independent of their order.
> 
> So in that case, the result should be a list of ordered pairs like: 
> [("egg", 2), ("cheese", 1)]. Or a pair of two lists, like (["egg", 
> "cheese"), (2,1)]. Otherwise you would not know which frequency belongs 
> to which element?
> 
> I can't write this concisely nor efficient yet, but the following does 
> the job:
> 
> import Data.List
> 
> freq xs = zip e f
>   where
>     s = sort xs
>     e = nub s
>     f = map length (group s)
> 
> However, I suspect the experts here will be able to make that much 
> shorter and more efficient (maybe using Data.Map?)
> 
> Peter
> 
> 
> Stefan Holdermans wrote:
>> BH,
>>
>>> Is there a library function to take a list of Strings and return a 
>>> list of
>>> ints showing how many times each String occurs in the list.
>>>
>>> So for example:
>>>
>>> ["egg", "egg", "cheese"] would return [2,1]
>>
>> freq xs = map length (group xs)
>>
>> HTH,
>>
>>   Stefan
>> _______________________________________________
>> Haskell-Cafe mailing list
>> Haskell-Cafe at haskell.org
>> http://www.haskell.org/mailman/listinfo/haskell-cafe
>>
>>
> 
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
> 
> 

-- 
View this message in context: http://www.nabble.com/Suspected-stupid-Haskell-Question-tf4639170.html#a13251343
Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.