[Haskell-cafe] Printing the empty list.

Joshua Ball joshbball at gmail.com
Fri Jul 1 00:58:15 CEST 2011


GHCi seems to be clever about some things:

If I try to print the empty list in ghci, I encounter no problems:

Prelude> []
[]
Prelude> show []
"[]"
Prelude> print []
[]

Even though the type of the list is clearly unknown, it must be
picking SOME type. (why does it print [] instead of "")?

If I write a program in a file and load it in

main = print []

Then I get the ambiguous type variable error that I would expect. Why
doesn't ghci generate this error at the prompt?

-- 
Borrow my books: http://goo.gl/UBbSH



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