Deleting the second element in tuples

I have a list of tuples that look like this.

[ [(1,True),(2,True)] , [(3,False),(4,False),(5,False)] ]

My goal is so get [1,2,3,4,5] of out that mess.

I tried to use map and filter to remove all the Bools but filter also removed the first element in 开发者_StackOverflow中文版the tuple. If I can remove the Bools in each tuple then I can maybe use a loop to assign fst of each tuple to a new empty list?

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f :: [[(a, b)]] -> [a]
f = concatMap (map fst)

Then f [ [(1,True),(2,True)] , [(3,False),(4,False),(5,False)] ] is [1,2,3,4,5].

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Or with list comprehensions:

f xss = [fst x | xs <- xss, x <- xs]

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Try this (edited, thanks to Michael Kohl's and pat's comments):

fun :: [[(a,b)]] -> [a]
fun = map fst . concat

Then in GHC:

*Main> let l = [ [(1,True),(2,True)] , [(3,False),(4,False),(5,False)] ]
[[(1,True),(2,True)],[(3,False),(4,False),(5,False)]]
*Main> fun l
[1,2,3,4,5]

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foldl1 (\acc x -> acc ++ x)  [a | b <- lst, let a =  map fst b]