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The Ruby Programming Language

Cover of The Ruby Programming Language by Yukihiro Matsumoto... Published by O'Reilly Media, Inc.
  1. The Ruby Programming Language
    1. SPECIAL OFFER: Upgrade this ebook with O’Reilly
    2. A Note Regarding Supplemental Files
    3. Preface
      1. Acknowledgments
      2. Conventions Used in This Book
      3. Using Code Examples
      4. How to Contact Us
      5. Safari® Enabled
    4. 1. Introduction
      1. A Tour of Ruby
      2. Try Ruby
      3. About This Book
      4. A Sudoku Solver in Ruby
    5. 2. The Structure and Execution of Ruby Programs
      1. Lexical Structure
      2. Syntactic Structure
      3. File Structure
      4. Program Encoding
      5. Program Execution
    6. 3. Datatypes and Objects
      1. Numbers
      2. Text
      3. Arrays
      4. Hashes
      5. Ranges
      6. Symbols
      7. True, False, and Nil
      8. Objects
    7. 4. Expressions and Operators
      1. Literals and Keyword Literals
      2. Variable References
      3. Constant References
      4. Method Invocations
      5. Assignments
      6. Operators
    8. 5. Statements and Control Structures
      1. Conditionals
      2. Loops
      3. Iterators and Enumerable Objects
      4. Blocks
      5. Altering Control Flow
      6. Exceptions and Exception Handling
      7. BEGIN and END
      8. Threads, Fibers, and Continuations
    9. 6. Methods, Procs, Lambdas, and Closures
      1. Defining Simple Methods
      2. Method Names
      3. Methods and Parentheses
      4. Method Arguments
      5. Procs and Lambdas
      6. Closures
      7. Method Objects
      8. Functional Programming
    10. 7. Classes and Modules
      1. Defining a Simple Class
      2. Method Visibility: Public, Protected, Private
      3. Subclassing and Inheritance
      4. Object Creation and Initialization
      5. Modules
      6. Loading and Requiring Modules
      7. Singleton Methods and the Eigenclass
      8. Method Lookup
      9. Constant Lookup
    11. 8. Reflection and Metaprogramming
      1. Types, Classes, and Modules
      2. Evaluating Strings and Blocks
      3. Variables and Constants
      4. Methods
      5. Hooks
      6. Tracing
      7. ObjectSpace and GC
      8. Custom Control Structures
      9. Missing Methods and Missing Constants
      10. Dynamically Creating Methods
      11. Alias Chaining
      12. Domain-Specific Languages
    12. 9. The Ruby Platform
      1. Strings
      2. Regular Expressions
      3. Numbers and Math
      4. Dates and Times
      5. Collections
      6. Files and Directories
      7. Input/Output
      8. Networking
      9. Threads and Concurrency
    13. 10. The Ruby Environment
      1. Invoking the Ruby Interpreter
      2. The Top-Level Environment
      3. Practical Extraction and Reporting Shortcuts
      4. Calling the OS
      5. Security
    14. Index
    15. About the Authors
    16. Colophon
    17. SPECIAL OFFER: Upgrade this ebook with O’Reilly
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Numbers and Math

Chapter 3 covered the various Numeric subclasses in Ruby, explained how to write numeric literals in Ruby, and documented Ruby’s integer and floating-point arithmetic. Here we expand on that chapter to cover numeric APIs and other math-related classes.

Numeric Methods

Numericand its subclasses define a number of useful predicates for determining the class or testing the value of a number. Some of these predicates work only for Float values, and some work only for Integervalues:

# General Predicates
0.zero?        # => true (is this number zero?)
1.0.zero?      # => false
0.0.nonzero?   # => nil (works like false)
1.nonzero?     # => 1 (works like true)
1.integer?     # => true
1.0.integer?   # => false
1.scalar?      # => true: not a complex number. Ruby 1.9.
1.0.scalar?    # => true: not a complex number. Ruby 1.9.
Complex(1,2).scalar? # => false: a complex number. require 'complex' in 1.8

# Integer predicates (Ruby 1.9 and 1.8.7)
0.even?        # => true
0.odd?         # => false

# Float predicates
ZERO, INF, NAN = 0.0, 1.0/0.0, 0.0/0.0  # Constants for testing

ZERO.finite?   # => true: is this number finite?
INF.finite?    # => false
NAN.finite?    # => false

ZERO.infinite? # => nil: is this number infinite? Positive or negative?
INF.infinite?  # => 1
-INF.infinite? # => -1
NAN.infinite?  # => nil

ZERO.nan?      # => false: is this number not-a-number?
INF.nan?       # => false
NAN.nan?       # => true

Numeric and its subclasses define various methods for rounding numbers:

# Rounding methods 1.1.ceil # => 2: ceiling: smallest integer >= ...

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