Re: sort function

From: Thomas A. Russ (tar_at_sevak.isi.edu)
Date: 01/05/04 

Date: 05 Jan 2004 10:53:39 -0800

I seem to be missing part of this thread. I hope I'm not being too
repetitive here.

Dave Seaman <dseaman@no.such.host> writes:

>
> On Fri, 2 Jan 2004 14:49:31 -0000, Steve Ellis wrote:
> > Hi again
>
> [1]> (sort '((9 a) (3 b) (4 c)) #'(lambda (x y) (< (car x) (car y))))
> ((3 B) (4 C) (9 A))

An easier to understand Common Lisp formulation would be to take
advantage of the :key keyword argument to sort for this sort of
comparison operation:

(sort '((9 a) (3 b) (4 c)) #'< :key #'car)

It seems to more modularly declare the intention of the programmer to
sort using the < predicate applied to the CAR of the data structures.

(For completeness I would also worry about destructively modifying a
constant list argument, but for an example it's not worth sweating). 

-- 
Thomas A. Russ,  USC/Information Sciences Institute

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