[Haskell-beginners] some terminology

Brandon S. Allbery KF8NH allbery at ece.cmu.edu
Wed Aug 12 22:04:40 EDT 2009

On Aug 12, 2009, at 21:59 , Michael P Mossey wrote:
> I was looking at some code, saw a variable x, and said to myself,  
> "Ah that variable is a monad." Then I realized "Monad" is the name  
> of a type class. So maybe x should be called "an instance of a  
> Monad." I think the word "instance" in this case is OO-like; but in  
> Haskell "instance" refers to a type that is an instance of a type  
> class. Or maybe it can refer to both? And Monad is a type class, not  
> a type. Maybe I need the phrase "monadic type" to refer to an  
> instance of a type class. So maybe x is just "a variable of a  
> monadic type"?

Strictly speaking, yes.  In practice the common shorthand is "in the X  
monad" or just "in X".

brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university    KF8NH

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