real-life identity and "=="

Michael Hudson mwh21 at cam.ac.uk
Sun May 14 21:32:43 CEST 2000


weeks at golden.dtc.hp.com ((Greg Weeks)) writes:

[schnipp]
> Now, I agree that comparing the *contents* of lists is sometimes useful.
> But "==" should not be the way to do it (just as "=" is not the way to copy
> contents).
> 
> In practice, it doesn't much matter.  But it itches.  So close!
> 
> Greg
> 
> PS: Java has a similar problem.  For BitSets for example, the equals() and
> hashCode() methods erroneously assume immutability.  Again, so close.

Common Lisp has eq, eql, equal and equalp which are all different ways
of testing equality - and that's probably not enough for a completely
general solution.  There is a reason for this; equality is not as
clearly a defined operation as one might think.

BTW, eql is almost exactly what you are asking for in Python.

unhelpful-ly y'rs
m.

-- 
40. There are two ways to write error-free programs; only the third
one works.
     -- Alan Perlis, http://www.cs.yale.edu/~perlis-alan/quotes.html



More information about the Python-list mailing list