What's the point of 'const' in the Haskell Prelude?

Question

Looking through the Haskell Prelude, I see a function const:

const x _ = x

I can\'t seem to find anything relevant regarding t

Answer 1

Say you want to create a list of Nothings equal to the length of a string. As const returns its first argument, no matter the second, you can do:

listOfNothings :: String -> [Maybe Char]
listOfNothings = (map . const) Nothing

or, more explicitly:

listOfNothing st = map (const Nothing) st