Re: Guidelines for the "symbol" syntax class

[Dmitry Gutov]

On 01/04/2016 04:21 AM, John Yates wrote:
> On Sun, Jan 3, 2016 at 8:35 PM, Dmitry Gutov <address@hidden
> <mailto:address@hidden>> wrote:
>  >
>  > => [:<=>, :==, :===, :eql?, :hash, :casecmp, :+, :*, :%, :[], :[]=,
> :insert, :length, :size, :bytesize, :empty?, ...]
>
> It seems similar to C++'s operator keyword.  Am I getting closer?  Is
> the colon required to abut the subsequent characters or can one write :
> <=> (note intervening space)?

No space allowed. See this usage example:

irb(main):003:0> "abc" == "def"
=> false
irb(main):004:0> String.instance_method(:==)
=> #<UnboundMethod: String#==>
irb(main):005:0> "abc".size
=> 3
irb(main):006:0> String.instance_method(:size)
=> #<UnboundMethod: String#size>
irb(main):007:0> "abc".method(:size)
=> #<Method: String#size>
irb(main):008:0> "abc".method(:size).call
=> 3

You can have Symbols with any name, though. So they are not tied to 
methods, variables or anything.

Here's a good explanation: 
http://www.randomhacks.net/2007/01/20/13-ways-of-looking-at-a-ruby-symbol/, 
in particular, comparison #6 rings true: Ruby Symbols are similar to 
Lisp symbols. In Lisp, one can reference a dynamically bound variable, 
or call a function, using a symbol:

(let ((sym 'car)) (funcall sym nil))

or even

(let ((sym 'car)) (funcall (symbol-function sym) nil))

which is similar to "abc".method(:size).call I've tried above.