I was surprised to discover that the code

    astring.sub!(/hi/, 'bye')

behaves subtly differently from

    astring = astring.sub(/hi/, 'bye')

Intuitively, to me, these should be identical. Perhaps the documentation
should make mention of this difference? A note about this unexpected
behavior would have saved me a lot of frustration, and would likely do
the same for many others new to Ruby.

To be honest, I'm still trying to find out exactly why these do
different things. The difference does not manifest itself with trivial
cases in irb; rather it shows up when I'm getting a string from cgi,
modifying it, then inserting it into a database. When using sub!, the
database ends up containing the pre-sub'd value of astring, even though
astring appears to contain the modified version when printed with a
debug statement immediately preceding my database insert.

I'm willing to except the criticism that my intuition is perverse in
some way, but when I started writing in Ruby I was really hoping it
would be a language one could use without having to understand how the C
underneath it all worked (defeating part of the purpose of "high level"
languages).

So what do you think? Would warnings in the documentation on exclamation
functions be useful or pointless?
-- 
Posted via http://www.ruby-forum.com/.