I don't know what this tuple is representing, but if you want to group you'll
have to specify on 'what':
- the tuple,
- the fst or
- the snd
Here's a possibility with grouping on the fst
import Data.List
import Data.Ord
import Data.Function
groupAtoms ::
(Float -> Bool)
-> [(Float,Integer)]
-> ([[(Float,Integer)]],[[(Float,Integer)]])
groupAtoms p = partition (p.sum. map fst). groupBy ((==)`on`fst). sortBy
(comparing fst)
Use:
groupAtoms (>=1.0) myList
If this is what you want: proper lists are in the fst of the result.
Hallo João Paulo Pizani Flor, je schreef op 23-11-10 18:23:
Hello dear Haskellers!
I've been a user and big fan of Haskell for a while, but only now I'm writing
my first "big" project in Haskell (some thousands of lines of code perhaps).
It's an interpreter for a programming language, the source code is music! Yes,
sheet music! :D
OK, so my specific problem goes like this: I have a list of tuples
:t myList
[ (Float, Integer) ]
And I want to "group" this list into a nested list
groupAtoms :: [ (Float,Integer) ] -> [ [(Float,Integer)] ]
Of course, I want that the concatenation of the groups yield me the original
list, i.e, (foldl (++) [] . groupAtoms == id), and the criterion that defines
a group is that:
"The sum of the first elements in the tuples comprising the list must be
greater than or equal to 1.0". That is, given a list of tuples, the boolean
predicate deciding whether this list is a PROPER group (True) or TOO SMALL
(False) is:
\g -> sum (map fst g) >= 1.0
Although the criterion is very clear, I've tried hard until now and couldn't
come up with a function for producing the nested list based on this grouping
criterion. I am sure that the Haskell Hierarchical Libraries have something
to help me, but only now I see I'm still a big noob :P
Could someone please help me writing this function?
My best regards from Brazil,
João Paulo Pizani Flor
[email protected] <mailto:[email protected]>
Federal University of Santa Catarina
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