[clean-list] (+) is a binary function

[Thomas van Noort]

Hi,

The signature from the Clean Book is correct, + is not only a binary
function but also a type class taking one type argument (as defined on
page 16):

class (+) infixl 6 a :: a a -> a

The confusion might originate from the fact that this definition is
shorthand notation for:

class + a where
   (+) infixl 6 :: a a -> a

This definition clarifies the fact that + is a binary function taking two
arguments and a type class as well taking a single type argument.

The shorthand notation is probably introduced for type classes that only
define a single function with the same name as the type class.

Regards,
Thomas

terrence.x.brannon at jpmchase.com wrote:
> 
> This seems like an obvious statement, but I am reading the Clean Book 
> and saw this annotation for double:
> 
>     double :: a -> a | + a
> 
> which reads as "double is a function which takes an argument of type a 
> and returns and value of type a provided that a version of + is defined 
> which can handle arguments of type a"
> 
> But my question is: since (+) is a binary function, shouldnt that read:
> 
>    double :: a -> a | + a a
> 
> 
> --
> Terrence Brannon - SID W049945
> 1111 Polaris Pkwy, OH1-1141, Columbus, OH 43240
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