Haskell Error Reporting

Question

I have a Haskell function that reports a long error message. Although I can write this message on one line, I want to split it into two or more, for example.

foo ab | a > b = a | a == b = b | otherwise = error "Blah blah blah blah in this line and some more blah in this line also." 

GHCi will not compile it. Any suggestion? Random googleing did not give any answer.

Answer 1

you can just concatenate strings:

 foo ab | a > b = a | a == b = b | otherwise = error ("Blah blah blah blah in this line and" ++ " some more blah in this line also.") 

it works for me

Answer 2

You can use the ghc multi-line string syntax for this:

 foo ab | a > b = a | a == b = b | otherwise = error "Blah blah blah blah in this line and \ \some more blah in this line also." 

For errors, this does not really matter, but in other contexts it can be more efficient than string concatenation.