The Top-Level Environment
When the Ruby interpreter starts, a number of classes, modules, constants, and global variables and global functions are defined and available for use by programs. The subsections that follow list these predefined features.
Predefined Modules and Classes
When the Ruby 1.8 interpreter starts, the following modules are defined:
Comparable FileTest Marshal Precision Enumerable GC Math Process Errno Kernel ObjectSpace Signal
These classes are defined on startup:
Array File Method String Bignum Fixnum Module Struct Binding Float NilClass Symbol Class Hash Numeric Thread Continuation IO Object ThreadGroup Data Integer Proc Time Dir MatchData Range TrueClass FalseClass MatchingData Regexp UnboundMethod
The following exception classes are also defined:
ArgumentError NameError SignalException EOFError NoMemoryError StandardError Exception NoMethodError SyntaxError FloatDomainError NotImplementedError SystemCallError IOError RangeError SystemExit IndexError RegexpError SystemStackError Interrupt RuntimeError ThreadError LoadError ScriptError TypeError LocalJumpError SecurityError ZeroDivisionError
Ruby 1.9 adds the following modules, classes, and exceptions:
BasicObject FiberError Mutex VM Fiber KeyError StopIteration
You can check the predefined modules, classes, and exceptions in your implementation with code like this:
# Print all modules (excluding classes) puts Module.constants.sort.select {|x| eval(x.to_s).instance_of? Module} # Print all classes (excluding exceptions) ...Get The Ruby Programming Language now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
