joinString = zip "aceg" "bdfh"

Becomes this after zipping: [('a', 'b'), ('c', 'd'), ('e', 'f'), ('g','h')]. I want to extract the 'a' , 'c', 'e' and 'g' out from the list of tuples. How can I do that?

I tried fst(unzip joinString) but that gives me the string "aceg" but I want each and every of the characters individually.

CodePudding user response：

As noted in comments, a string is a list of characters, so you have a misunderstanding, but also already the answer.

ghci> ['a', 'b', 'c'] == "abc"
True

CodePudding user response：

Well, if you don't have direct access to the parameters supplied to zip, you can use map from Data.List to apply fst over every element of the zipped list:

ghci> map fst [('a', 'b'), ('c', 'd'), ('e', 'f'), ('g','h')]
"aceg"

As pointed out already, "aceg" == ['a', 'c', 'e', 'g'].