Re: [Haskell-cafe] A program which never crashes (even when a function calls "error")

On 8/1/06, Stephane Bortzmeyer wrote:

How to do it in Haskell? How can I call functions like Prelude.head while being sure my program won't stop, even if I call head on an empty list (thus calling "error")?

Try looking at Control.Exception. For example:

module Test where

import Control.Exception import Prelude hiding (catch)

example = (do print (head (tail "a")) return "ok") `catch` (\e -> do putStrLn ("Caught exception: " ++ show e) return "error")

produces: *Test> z <- example Caught exception: Prelude.head: empty list *Test> z "error" This might be the beginning of what you want. /g