What *are* variables? Which are nil now?

ruby-talk
21

svg% ruby -e ‘def nil.to_ary() [12] end; p +nil’
[12]
svg%

so why doesn’t this give the TypeError then?

Because, like I’ve said, Array#+ call #to_ary and because I’ve defined
^^^^^^^^^^^^^^^^^^^^
Ah, that was the bit I missed. Hmm, it’s only Array that defines
to_ary out of the box… Ah, [RubyTalk:72563] explains why there is
a to_a and a to_ary. This is much clearer now.

The only remaining aspect about this is why the traceback kept
flagging up the error as being in each rather than in the compact!
statement. … Ah, that’s because caller() means caller(1), not
caller(0). I think I see what is happening here.

nil#to_ary it just work

Guy Decoux

Thanks for your patience.

    Hugh
···

On Fri, 12 Sep 2003, ts wrote:

22

The only remaining aspect about this is why the traceback kept
flagging up the error as being in each rather than in the compact!

#compact! return nil if it don't modify the receiver : this is #compact!
  which return nil. With :

   @dirs += entries.collect{|f| stuff_here(f)}.compact!

ruby will do

   @dirs += nil

if #compact! don't modify the result of `entries.collect{...}'

Guy Decoux