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Ruby Programming
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Ruby names are used to refer to constants, variables, methods, classes, and modules. The first character of a name helps Ruby to distinguish its intended use. Certain names, listed in Table 18.3 on page 210, are reserved words and should not be used as variable, method, class, or module names.

Reserved words

__FILE__ and def end in or self unless
__LINE__ begin defined? ensure module redo super until
BEGIN break do false next rescue then when
END case else for nil retry true while
alias class elsif if not return undef yield

In these descriptions, lowercase letter means the characters ``a'' though ``z'', as well as ``_'', the underscore. Uppercase letter means ``A'' though ``Z,'' and digit means ``0'' through ``9.'' Name characters means any combination of upper- and lowercase letters and digits.

A local variable name consists of a lowercase letter followed by name characters.

fred  anObject  _x  three_two_one

An instance variable name starts with an ``at'' sign (``@'') followed by an upper- or lowercase letter, optionally followed by name characters.

@name  @_  @Size

A class variable name starts with two ``at'' signs (``@@'') followed by an upper- or lowercase letter, optionally followed by name characters.

@@name  @@_  @@Size

A constant name starts with an uppercase letter followed by name characters. Class names and module names are constants, and follow the constant naming conventions. By convention, constant variables are normally spelled using uppercase letters and underscores throughout.

module Math
  PI = 3.1415926
class BigBlob

Global variables, and some special system variables, start with a dollar sign (``$'') followed by name characters. In addition, there is a set of two-character variable names in which the second character is a punctuation character. These predefined variables are listed starting on page 213. Finally, a global variable name can be formed using ``$-'' followed by any single character.

$params  $PROGRAM  $!  $_  $-a  $-.

Method names are described in the section beginning on page 225.
Ruby Programming
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