This could do with some community input before going to the FAQ.
The format will be different but I just wanted to bang out some
content. I haven’t even checked if there is a question like this.
Can anyone think of a question title that does’t create confusion
with :name symbols?
[FAQ] What do you mean, <=!@/$!?
Half tongue in cheek.
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.
[Note: As I am defining these, I am going from most frequent to
least frequent use for the various default definitions.]
<=>, <=, <, >=, >, ==, !=
1. Relational operators, used to determine the relative
equality of values. All of these symbols, excepting “!=”,
are defined as methods on classes. The most common way of
implementing these values is through the [Comparable] mixin,
where it is only necessary to define “<=>” (which must
return a value of -1, 0, or +1). All other relational
operators, if defined manually, must return a boolean value
(either FalseClass or TrueClass). The “!=” operator is
special syntax in the interpreter, such that “a != b” really
means “!(a == b)”.
2. The “<” operator also means class inheritance, such that in
the following example, a Car inherits from Vehicle.
class Car < Vehicle; end
+, -, , /, %, **
1. Binomial arithmetic operators representing addition (3 + 2),
subtraction (3 - 2), multiplication (3 * 2), division (3 /
2), modulus (integer division remainder; 3 % 2 is 1), and
exponentiation (3 ** 2 is 9). “**” has the highest
precedence, followed by "", “/”, and “%”, and finally “+”
and “-”. All of these operators are methods.
2. Unary plus and minus (+3, -2). Unary plus and minus have
higher precedence than “*”, “%”, and “/”, but lower
precedence than “**”. These are methods (+@ and -@,
respectively).
~, <<, >>, &, ^, |
1. “<<” most often means that a “here” document follows, e.g.:
puts <<EOS
This is a here document.
EOS
2. "<<" also opens an object for modification to make a
singleton-object (one which is not quite like any other
object of its class). In the example below, only the Car
object referred to by "camaro" will have the method
"has_flames?".
camaro = Car.new
class << camaro
def has_flames?
true
end
end
3. Binary (bitwise) operators. "~" returns the bitwise
complement of the value (~2 is -3); "<<" and ">>" shift the
bits of the value left and right by the specified number of
bits (2 << 2 is 8 >> 2). "&", "^", and "|" are bitwise
"and" and exclusive and regular "or" operators.
···
On Sun, 1 Dec 2002 23:07:25 +0900, Gavin Sinclair wrote:
===
Case comparison operator. Used to select branches in case
statements.
., …
Range defnitions. “…” ranges are end-inclusive; “…” ranges
are end-exclusive. See [Range].
:, ?:, ::
1. Symbol mark. This marks the name as a Symbol, such that
:name is a Symbol. Most often used as a parameter to various
methods in the Module class, (e.g., public, private,
protected, attr_reader, attr_accessor, etc.). Symbols are
immutable, immediate value strings.
2. ?: is the ternary operator:
(boolean-test) ? (do-if-true) : (do-if-false)
3. :: resolves scope. ::Foo refers to a constant Foo at the top
level; Net::Ftp refers to a constant Ftp in the module (or
class) Net.
1. References an element of a collection. This is a method
call, defined as “”. Defining this method also gets
“=” for free.
2. Array definition, as in:
ndays = [ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 ]
{}, =>
Hash definition, most often used with “=>”. Can be used in one
of two ways. The example below will result in the same key/value
pairs. “=>” explicitly relates a key to a value; if => is not
used, then pairs are joined. An odd number of values will throw
an error, regardless of which method is used. The two methods
may not be mixed.
{ 1, 2, 3, 4, 5, 6 }
{ 1 => 2, 3 => 4, 5 => 6 }
!
Logical negation. Turns “false” to “true” and “true” to “false”.
=~, !~, //, %r{}
Regular expression handling. “=~” is a method, “!~” is special
syntax for “!(=~)”, like “!=”. // and %r{} have the same effect
in defining a regular expression. %r{} can be represented with
other characters. All of the following represent the same
regular expression. Note that if the first character following
“%r” is part of a matching pair ((), <>, , {}), then the
second character must be the matching character; otherwise, the
two characters must be the same.
/\d+/
%r{\d+}
%r/\d+/
%r@\d+/
%r(\d+)
#{}
String expression substitution. #{expr} substitutes the value of
expr in a double-quoted string (including regular expressions
and command strings). This can only be done with {}.
%q{}, %Q{}, %{}
Quotes, expressed another way. %q{} is equivalent to ‘’ and has
all the same semantics (no substitution excepting \ to \ and '
to '). %Q{} and %{} are equivalent to “” and have the same
semantics (full substitution, including expression substitution
with #{}). As with regular expressions, the {} in %q{} or %Q{}
can be represented with other characters.
%w{}
This will create an array from the string within by splitting
the string on spaces. The string is treated as a single-quoted
string.
%x{}
A command string. This behaves the same as backtick (``) command
execution.
-austin
– Austin Ziegler, austin@halostatue.ca on 2002.12.01 at 10.18.42
