Ruby Numbers

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Ruby provides a number of built-in number classes.

Notice: "built-in" in this case means you cannot use them explicitly.

Ruby's number objects keep the same object ID no matter the number class they fit at the momment.

Integer Class: The base class from which the following number classes are derived.

Fixnum Class: A Fixnum holds Integer values that can be represented in a native machine word (minus 1 bit). This effectively means that the maximum range of a Fixnum value depends on the architecture of the system on which the code is executing.

If an operation performed on a Fixnum exceeds the range defined by the system's machine word, the value is automatically converted by the interpreter to a Bignum.

Bignum Class: Bignum objects hold integers that fall outside the range of the Ruby Fixnum class. When a calculation involving Bignum objects returns a result that will fit in a Fixnum, the result is automatically converted to Fixnum.

BigDecimal Class: BigDecimal objects hold very large or very accurate floating point numbers. Decimal arithmetic is also useful for general calculation, because it provides the correct answers people expect.

Float Class: The Float object represents real numbers based on the native architecture's double-precision floating point representation.

Rational Class: Rational implements a rational class for numbers.

A rational number is a number that can be expressed as a fraction p/q where p and q are integers and q is not equal to zero. A rational number p/q is said to have numerator p and denominator q. Numbers that are not rational are called irrational numbers.

Let's see some of them in action.

      num = 43
      6.times do
        puts "#{num.class} #{num}"
        num *= num
      end
      

This will produce following result:

      Fixnum 43
      Fixnum 1849
      Fixnum 3418801
      Bignum 11688200277601
      Bignum 136614025729312093462315201
      Bignum 18663392025969146670022260524972832947786731075670401
      

 

Here are the ways you write numbers:

      puts 123456                    # Fixnum
      puts 123_456                   # Fixnum
      puts -543                      # Negative Fixnum
      puts 123_456_789_123_345_789   # Bignum
      puts 0xaabb                    # Hexadecimal
      puts 0377                      # Octal
      puts -0b101_010                # Binary (negated)
      

Notice: underscores are ignored.

This will produce following result:

      123456
      123456
      -543
      123456789123345789
      43707
      255
      -42
      

 

Here are some rational numbers:

      puts Rational(5,6)       # -> 5/6
      puts Rational(5)         # -> 5/1
      puts Rational(6,10)      # -> 3/5
      puts Rational.new!(6,10) # -> 6/10
      puts Rational(3,0)       # -> ZeroDivisionError
      

This will produce following result:

      5/6
      5
      3/5
      6/10
      D:/Ruby186-398/lib/ruby/1.8/rational.rb:72:
        in `reduce': denominator is zero (ZeroDivisionError)
      	from D:/Ruby186-398/lib/ruby/1.8/rational.rb:35:in `Rational'
      	from rubynumbers04.rb:5
      

 

Here are some BigDecimal numbers:

      require 'bigdecimal'
      
      puts BigDecimal('1876.8')
      a=BigDecimal('0.123456789123456789')
      b=BigDecimal('123456.78912345678',40)
      puts c = a + b
      

This will produce following result:

      0.18768E4
      0.123456912580245903456789E6
      

 

Converting Numbers in Ruby

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Numbers can be converted from one type to another using the Ruby Integer and Float methods. These methods take as an argument the value to be converted. For example:

      # Convert Floating Point Number to an Integer
      puts Integer(10.898)
      

      10
      

 

      # Convert a String to an Integer
      puts Integer("10898")
      

      10898
      

 

      # Convert a Hexadecimal Number to an Integer
      puts Integer(0xA4F5D)
      

      675677
      

 

      # Convert an Octal Number to an Integer
      puts Integer(01231)
      

      665
      

 

      # Convert a Binary Number to an Integer
      puts Integer(0b01110101)
      

      117
      

 

Convert a Character to the ASCII Character Code

For Ruby version 1.8 or earlier:

      puts Integer(?e)
      

      101
      

For Ruby version 1.9 or later:

      puts "e".getbyte(0)               #ASCII to Integer
      

      101
      

 

Similarly, we can perform conversions to floating point using the Float method:

      # Convert an Integer Floating Point
      puts Float(10)
      

      10.0
      

 

      # Convert a String to Floating Point
      puts Float("10.09889")
      

      10.09889
      

 

      # Convert a Hexadecimal Number to Floating Point
      puts Float(0xA4F5D)
      

      675677.0
      

 

      # Convert an Octal Number to a Floating Point
      puts Float(01231)
      

      665.0
      

 

      # Convert a Binary Number to Floating Point
      puts Float(0b01110101)
      

      117
      

 

Convert a Character to a Floating Point ASCII Character Code

For Ruby version 1.8 or earlier:

      puts Float(?e)
      

      101.0
      

For Ruby version 1.9 or later:

      puts "e".getbyte(0)
      

      101.0