show function

Hamilton Richards hrichrds at
Tue Dec 2 22:18:01 EST 2003

At 10:05 PM -0500 12/2/03, rui yang wrote:
>I want to print a function which itself have some functions as it's parameters
>and will return some functions as the results, and I want to print out the
>result, does anyone knows how to define the instance declaration of show class
>to this function type?

[moving to Haskell Cafe]

The mechanics of such an instance definition are simple enough. 
Letting F be your function type, this would do it:

>  instance Show F where
>    showsPrec f = ... some String ...

The hard question is what the result should be. Unlike the types 
already in Show (such as Bool, Int, Char, etc.), there's no canonical 
representation for functions (other than a complete list of 
argument-result pairs, which would not be very useful).


Hamilton Richards, PhD           Department of Computer Sciences
Senior Lecturer                  The University of Texas at Austin
512-471-9525                     1 University Station C0500
Taylor Hall 5.138                Austin, Texas 78712-0233
ham at                hrichrds at

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