[Haskell-cafe] list utilities -- shouldn't these be in the
hierarchical libs somewhere?
Twan van Laarhoven
twanvl at gmail.com
Tue Dec 18 11:13:39 EST 2007
Jules Bean wrote:
> Thomas Hartman wrote:
>> I found
>> had many useful "one off" type list functions such as "subsequences"
>> and "permutations" which are nowhere to be found in hoogle, Data.List,
>> or the haskell hierarchical libs
> It's not very many. Other that those, I spotted: sums, products,
> elemIndexBy, elemBy.
> I have no idea why they were removed between that version of the report
> and haskell98.
For the ones you mention:
- sums, products:
The names don't make it clear what they do, I could for instance
imagine sums being 'map sum'. And should it be a 'scanl' or 'scanr'?
- elemIndexBy, elemBy:
elemBy f x = any (f x)
elemIndexBy f xs x = findIndex (f x) xs
On the other hand, I would love to see "subsequences" and "permutations"
added to Data.List. In fact, I made a library proposal to make this
happen, hopefully they will be added to the standard library soon.
More information about the Haskell-Cafe