From: Michael Guterl <mguterl@...>
Date: 2009-01-05T00:32:12+09:00
Subject: Re: VERY simple question about "?"

On Sun, Jan 4, 2009 at 9:48 AM, Robert Klemme
<shortcutter@googlemail.com> wrote:
> On 04.01.2009 14:48, Tom Cloyd wrote:
>>
>> I guess what confused me is that I bring to Ruby the notion that if a
>> symbol causes something to happen, as "?" clearly does in my example (it
>> produces the integer code for a character),
>
> In this case nothing "happens" (see below).  It is just another syntactical
> way to express an integer constant.
>
>> its' an operator or method. I'm not unfamiliar with linguistics. I don't
>> see the equivalence between a string delimiter, or a character that signals
>> the beginning of a symbol, and a symbol that is actually productive of
>> something. Makes no sense to me at all, in fact. Maybe I'm failing to grasp
>> some transformative concept which changes how things work in the Ruby world.
>>
>> Seeing operators as methods makes some real sense, on the other hand. "="
>> produces something out of what it's given. It doesn't just change meaning,
>> which is all that happens with quotes or ":". That's the distinction I'm
>> seeing, and it seems valid.
>
> I am not sure what you mean by "change meaning".  Can you elaborate?
>
> Btw, note that there are two types of "=":
>
> 1. variable assignment as in "a = 123",
>
> 2. method call that mimics variable assignment as in "a.foo = 456".
>
> Both evaluate always to the right hand side - but this is about the only
> commonality.  Semantics of type 1 is fixed while you are free to implement
> type 2 in any way you like, e.g.
>
> irb(main):005:0> a = Object.new
> => #<Object:0x7ff79980>
> irb(main):006:0> def a.foo=(x) puts "bah!" end
> => nil
> irb(main):007:0> a.foo = 456
> bah!
> => 456
> irb(main):008:0>
>
>> I'll keep thinking about it.
>
> Basically "?a" is just another textual representation for the integer 97
> which happens to be the ASCII code of character "a".  It differs from string
> delimiters because the expression "foo" is actually a String constructor -
> it will create a new String object whenever it is executed:
>
> irb(main):003:0> 3.times { x = "foo"; puts x, x.object_id }
> foo
> 1073491940
> foo
> 1073492040
> foo
> 1073491880
> => 3
> irb(main):004:0>
>
>> Quite apart from this is the strange matter of how difficult it is to find
>> a simple, complete table of Ruby operators. I've basically given up on that.
>
> You can find it in the Pickaxe - a good book to have anyway.
>
>> Thanks for the Pickaxe reference - I found it on PDF p. 332 of my PDF
>> version of the 2nd ed. I'd never seen that page.
>
> As far as I know there is no legal electronic version of the second edition
> so you better double check whether you are allowed to use this.  You could
> as well buy the book to somewhat compensate for this.
>
http://www.pragprog.com/titles/ruby/programming-ruby

There definitely is an option to select a PDF version for purchase.