Re: [Haskell-cafe] IO is a bad example for Monads

On Dec 10, 2007 4:51 AM, Daniel Fischer wrote:

Am Montag, 10. Dezember 2007 10:36 schrieb Ketil Malde:

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Daniel Fischer writes:

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Various other people write:

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... lots of talk about monads and IO ...

When someone comes to me and says "I have this Python script that scans through these directories and finds the files that meet these criteria and generates a report based on this template, could I do it better in Haskell?" it'd be good to have a better answer than "to do this you could use the IO monad, but to do things properly you need to understand monads so here, learn about the List monad and the Maybe monad first, understand how this interface abstracts from both, come back when you've finished that, and then I'll tell you how to read and write files". And I definitely want a better answer than "Haskell I/O is performed using the IO monad but everyone thinks this is bad so just wait a few years and someone may write a fancy new nice combinator library that does exactly what you want". There are thousands of competing programming languages out there, and there are dozens that are viable choices for the task I just mentioned. If my response to their question takes longer than the time it would take to find another language and implement a solution, then Haskell will remain a niche language. Maybe hardened Haskell programmers don't notice these things, but there's a wall that goes up when Haskell is presented to non-functional programmers. There are significant barriers for them to cross (some of them imaginary): there's the infamous type system, there's the mystique around monads, there's the fear that laziness can impact performance, the general fear that many ordinary programmers have about recursion, and so on. Giving people even the slightest reason to think that there's something weird about opening files or printing a result is just another brick in that wall, and it's probably the biggest brick of all. -- Dan