Re: Adding an ignore function to Control.Monad

On Thu, Jun 11, 2009 at 08:57:31PM +0200, Henning Thielemann wrote:

On Thu, 11 Jun 2009, David Menendez wrote:

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On Thu, Jun 11, 2009 at 1:53 PM, Sittampalam, Ganesh wrote:

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do _ <- getLine   return 3

Ganesh

Again, why do you think that? I much prefer the current syntax.

http://haskell.org/haskellwiki/Restrict_type_of_monadic_binding http://haskell.org/haskellwiki/Do_notation_considered_harmful#Safety

And here I always get annoyed by types that specify '()' explicitly when a universally quantified type will do. (`when` and `unless` are particularly offensive in this regard). Forcing idioms to be more verbose than necessary obscures intent. Do we have any data that accidentally ignoring return values is a problem in practice? I don't mean as it confused someone once and then they learned their lesson. Because changing the type of (>>) would imply extra effort always for everyone, whereas remembering that return values might be important isn't exactly a recurring problem. It may save someone a bug once when using System.system, but cause enough other code to be obscured in meaning to hide a dozen other bugs. The fact you currently don't assign a value to something means you probably would have just mistakenly used 'ignore' in any case. Also, treating '()' specially as 'don't care' as opposed to any other unit type doesn't sit right with me either. Sure it is an obvious choice for a don't care value, but the fact you can use others is nicely consistent with the idea that other than having some syntatic sugar, built in types are not special in haskell. John -- John Meacham - ⑆repetae.net⑆john⑈ - http://notanumber.net/