[Paticia]

Heeeeeeeeeeeelp plssssss.

Well, I have a beginner problem (for me, atm, is a very advanced problem ).

I have a list of tuples, like:

x = [("a","b","c"),("d","e","f")] 

… and I need to change, let’s say, the "e" for "xyz". Can it be done?

I’ve tried to apply pattern matching, but with no success.
With tuples of 2 elements it’s easier (by using fst and snd)… but I’m having lots of problems with tuples of 3 elements.
Is pattern matching the right way to solve this?

Any help will be welcome.
Thanks in advanced.

[sepp2k]

I'm not quite sure what you're trying to do here. Can you show us how you would do it with 2-tuples using first and second? That might make it clearer what you're trying to accomplish.

[Paticia]

If I have, for example,

tuplelist1 = ("a","b")

and I wanna change "a" for "xyz":

tuplelist2 y = (fst tuplelist1, y)

then:

ghci> tuplelist2 "xyz"
("a","xyz")

... but I need it for 3-tuple ... in a list, like: x = [("a","b","c"),("d","e","f")]

[sepp2k]

Okay, the 3-tuple equivalent of your code is:

tuplelist1 = ("a", "b", "c")
change (x, _, _) y z = (a,b,c)
tuplelist2 y z = change tuplelist1 y z

I.e. you do indeed use pattern matching to replace fst and snd.

[Paticia]

That's a great help.

It seams so easy... :S

thank you very much!