CODEWITHSUNDEEP
haskell
Dilawar
Dilawar

Reputation: 5645

Multiline error message reporting in Haskell

I have a Haskell function which reports a long error message. Although I can write this message in one line, I want to break it into two or more e.g.

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

GHCi does not compile it. Any suggestion? A casual googleing did not produce any answer.

Upvotes: 4

Views: 311

Answers (2)

John L
John L

Reputation: 28097

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

foo a b | 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 it doesn't matter much, but in other contexts it can be more efficient than concatenating strings.

Upvotes: 6

Random Dev
Random Dev

Reputation: 52290

you can just concatenate the strings:

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

this works for me

Upvotes: 3

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