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I have a list of lists, let's say:
import Data.List
xs = [[1,2], [1,2,3], [2,3]]
I want to get the inner list with the most items, in this case [1,2,3].
I'm trying to use the maximumBy function from the Data.List library:
maximumBy (compare `on` length) xs
but I get the following error: not in scope 'on'
Can anyone tell me what is wrong, or if you have a better way to get the list?
301
Python sort() method and == operator to compare lists We can club the Python sort() method with the == operator to compare two lists. Python sort() method is used to sort the input lists with a purpose that if the two input lists are equal, then the elements would reside at the same index positions.
Technique 1: The len() method to find the length of a list in Python. Python has got in-built method – len() to find the size of the list i.e. the length of the list. The len() method accepts an iterable as an argument and it counts and returns the number of elements present in the list.
To get the length of a list in Python, you can use the built-in len() function. Apart from the len() function, you can also use a for loop and the length_hint() function to get the length of a list.
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The len () method offers the most used and easy way to find length of any list. This is the most conventional technique adopted by all the programmers today. # Python program to demonstrate working # of len ()
or you can make it a bit more explicit:
xs = [[1,2],[1,2,3],[2,3]]
ordLen a b = compare (length a) (length b)
maximumBy ordLen xs
maybe it's easier to understand this way.
80
on is defined in Data.Function, so you need to import that.
Alternatively, you can use comparing from Data.Ord:
maximumBy (comparing length) xs
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