From: Dave Thomas <Dave@...>
Date: 2001-09-04T07:14:24+09:00
Subject: [ruby-talk:20818] Re: RCR: non-bang equivalent to []=

Tobias Reif <tobiasreif@pinkjuice.com> writes:

> AFAIK, there are many more methods that are destructive but don't
> declare that in their name:
> clear, delete, delete_at, delete_if, fill, pop, push, replace, shift,
> unshift, Array#filter.
> 
>...
>
> Something like "Beware, however, that there are a fair number of
> destructive methods that don't have an '!' " in the FAQs it not a
> nice discovery for everyone learning Ruby.  "The plain version takes
> a copy of the receiver, makes its change to it, and returns the
> copy. The version with the ! modifies the receiver in place."  is a
> rule with many non-obvious exceptions.  This fact which generates
> confusion, and sabotages the "Princple of Least Surprise" in a very
> relevant way.

Being realistic, though, wouldn't you expect

  a[1] = 2

to modify the object referenced by 'a'. Similarly for 'delete' and
company.

There _are_ issues with '!', particularly to do with return values
when the receiver isn't changed, but I don't think you should take the
'!' as a part of the semantic content of the method being called. It
really is no more than a hint that something "dangerous" is going on.


Regards


Dave