[Haskell-cafe] do

jerzy.karczmarczuk at info.unicaen.fr jerzy.karczmarczuk at info.unicaen.fr
Sun Oct 14 05:43:02 EDT 2007

Andrew Coppin writes: 

> PR Stanley wrote:
>> What is the role of ">>"?
>> How is ">>" different to ">>="? I am aware that ">>=" is used for 
>> sequencing parsers but that's all I know about it.
> foo >>= bar 
> executes the action "foo" and passes its result to the function "bar" 
> (which must then return another action, which is executed). 
> foo >> bar 
> executes the action "too", and then executes the action "bar". Any result 
> generated by "foo" is discarded


I believe that our - sometimes helpful, sometimes not - answers should
regularly encourage the newbies to *READ* the tutorials, the documentation,

My goodness, is it really too difficult? Then, the answer would be given
by the default definition in the Prelude: 

 -- Minimal complete definition:
m >> k  =  m >>= \_ -> k 

which means exactly that, >>= is the base, >> uses it, but doesn't care
about the argument. And shows that the verbal explanation, "actions",
"executed", etc. may not be true in general 

I know that asking helpful humans is nicer than reading docs, but the latter
is usually more instructive, and often more efficient. 

Jerzy Karczmarczuk 

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