From: Gavin Sinclair <gsinclair@...>
Date: 2002-12-02T00:01:45+09:00
Subject: [FAQ] [Revised] What do some of Ruby's symbols mean?

Thanks for the instant feedback.  And apologies for the offensive late-night
manager humour.  If only I'd limited it to my workplace... .  Aside: I actually
find it difficult to come up with an example for the ternary operator, as I
don't consider it "the Ruby way".

Here's the revision.

---

Q: What do some of Ruby's symbols mean?

A:

This question is about non-aplhanumeric characters in Ruby code, not about
*symbols* like :name.  For those, see [appropriate link].  Actual explanations
of the concepts behind them is beyond the scope of this answer.

<= < != == > >>
   Relational operators, as per most other computer languages.  Are often
   redefined for use with various classes.

+ - * / %
   Common arithmetic operators.  Some are defined also for String, Array
   and others.

===
   Case comparison operator.  Used to select branches in case statements.

<
   Class inheritance, as in
     class Car < Vehicle
     end

<<
   Singleton definition.  See [appropriate link] for more info.
   Also commonly used as a method for appending (e.g. Array and String).

.. ...
   Range definers, as in 0...10 and "a".."z"

:
   Symbol definer, as in :name, where :name.to_s == "name".  See [a/l].
   See next item also.

?:
   Ternary decision operator, as in C.  For example:
     return (level == DEBUG) ? "" : detailed_info

{} =>
   Hash definition, as in
     numstr = { 1 => "one", 2 => "two", ... }

[]
   Array definition, as in
     ndays = [ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 ]

%w[]
   String-Array converter, as in
     dayabbrev = %w[Sun Mon Tue Wed Thu Fri Sat]
     dayabbrev == ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]

//
   Regular expression definition, as in
     date_re = /(\d\d\d\d)-(\d\d)-(\d\d)/
     y, m, d = date_re.match("2002-12-01")[1..3]

?!
   Suffixes for methods (optional, of course).  In general:
     method!   changes the object (e.g. String.gsub!)
     method?   returns boolean    (e.g. Array.empty?)