CODEWITHSUNDEEP
haskell
user606521
user606521

Reputation: 15434

no parse exception

I am trying to cach exception caused by read function:

run :: CurrentData -> IO ()
run current = do
{
    x <- (getCommandFromUser) `E.catch` handler;
    updated <- executeCommand x current;
    run updated;    
} where handler :: E.IOException -> IO Command
    handler e = do putStrLn "wrong command format" >> return (DoNothing);

In this code function getCommandfrom user gets some string from user and then tries to read some data from this string using "read" function

If read fails there is exception thrown: 

*** Exception : prelude.read : no parse

and program exits... I can't catch this exception - what is type of this exception???

I tried also E.SomeException instead of E.IOException...

E is from import Control.Exception As E

Upvotes: 2

Views: 573

Answers (1)

Daniel Fischer
Daniel Fischer

Reputation: 183898

"what is type of this exception?" The type is ErrorCall, also available from Control.Exception. An ErrorCall is what is thrown when the error function is called. Just change the type of handler and it will work. A last resort to get things working is to catch E.SomeException, but that's almost always the wrong thing to do.

Upvotes: 1

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