Ruby Code Examples

This page illustrates the Ruby Code Examples, in a straight way than to lengthy explanations, this can be used like an immediate reference for both syntax and programming ideas. Concise mothods attempting a problem with a pragmatic approach are also discussed.

Basics

Simple I/O

puts 'Hi!'                   # puts the string to stdout
print 'enter your name:'     # print does not terminate with default \n at the end of execution
name = gets.chomp            # read from stdin
puts "Hi! #{name}"           # interpolates the string, replaces name with its value

Strings

print 'c:\books\net\apps\tools'    # outputs, c:\books\net\apps\tools
print "c:\books"                   # outputs, cooks

String interpolation allows a variable to get replaced by its value while execution

One = 1
puts "#{One} is a number"      # outputs, 1 is a number
puts "%d is a number" % One    # outputs, 1 is a number

%Q and %q are string literals that are with special properties

puts %Q^ is Quote friendly^
puts %q# you can type "Quotes"!! #    # outputs, you can type "Quotes"!!

Multiline Strings are defined with '<<' prefix to a named delimiter, like

puts <<XYZ
Normally programmers try to code to solve the problem and forgets once it is done,
but some explore more, to find a concise opproach to the problem,
and thats makes him !(repetative)
XYZ

Ruby is really flexible with strings

# choose the one you like
' this '
" this "
%/ this /
%q{ this }
%Q^ this ^
# value => " this "

The string delimiter pairs are '', "", but with %, %q and %Q prefix, we have //, {}, ##, as delimiters, the unofficial rule is to use the delimiter that is not used to declare the string itself, this is to declare raw strings to avoid delimiter collision

puts %/ '' "" {} ## ^^ /    # outputs,  '' "" {} ## ^^

Objects

An Object is something that can be handled with defined Methods, even for the physical objects arround us there are defined methods in using them, whenever we say 'object' it is to mean that it has some methods through which the object can be handled

-1.abs                               # => 1
'1234567'.length                     # => 7 
1234567.to_s.length                  # => 7
3.times {print 3}                    # outputs, 333
rand(10).times { |x| puts "#{x}"}    # is !infinite, why? = find

Ruby is object oriented, everything is an object including numbers, strings and even the nil

1.class        # => Fixnum
1.0.class      # => Float
'xyz'.class    # => String
nil.class      # => NilClass

Enumerators, Ranges, Arrays and Hashes

Each of these can use the each method for iteration, though they seems to be synonyms, there is lot of difference in computing, The Enumerators and Ranges are almost of fixed memory length and so are memory efficient and fast, whereas Arrays and Hashes involves complex data structures for to be dynamic

Enumerators

5.times.class       # => Enumerator
5.upto(10).class    # => Enumerator
5.upto(10).next     # => 5

Ranges

(0...10).class    # => Range
(0..9).class      # => Range
(0..2).first      # => 0
(0..2).last       # => 2 
(1..5).next       # invalid, Range class doesent have next method
 
(0..3).each { |x| print x }              # outputs, 0123
(0...10).reverse_each { |x| print x }    # outputs, 9876543210
(-3..3).each.abs { |x| print x }         # invalid
(-3..3).each { |x| print x.abs }         # outputs, 3210123
 
# Enumerator dosent require 'each' to iterate
5.upto(10).class                         # => Enumerator
5.upto(10) { |x| print x }               # outputs, 5678910 
(5..10).each { |x| print x }             # outputs, 5678910

Arrays

An array is a collection of elements, by default an array of n elements has its index enumerated from 0 to n-1, i.e, the index to the first element of an array is 0

a = [4,6,7,5]    # simple array declaration 
a.length         # => 4
a.rotate         # => [6, 7, 5, 4]
a.sort           # => [4, 5, 6, 7]
a.sort.reverse   # => [7, 6, 5, 4]
a[0]             # => 4
a[3]             # => 5
a[4] = 3         # => 3 ;resulting array is [4, 6, 7, 5, 3]
a << 1           # => [4, 6, 7, 5, 3, 1] ; useful when array size is unknown
a[10] = 0        # => 0 ;resulting array is [4, 6, 7, 5, 3, 1, nil, nil, nil, nil, 0]
a.length         # => 11

array of arrays, array of ranges and arrays of mixed datatypes are allowed to declare, Object Oriented!

hex = [(0..9),('A'..'F')]
hex.each { |x| x.each { |y| print y }}    # outputs, 0123456789ABCDEF
 
# declare an array of arrays
nums = [[0,1], [2,3,4,5,6,7], [8,9], ['A','B','C','D','E','F']]
binary = nums[0]                         # => [0, 1]
octal = nums[0] + nums[1]                # => [0, 1, 2, 3, 4, 5, 6, 7]
decimal = nums[0] + nums[1] + nums[2]    # => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
hexadecimal = nums.flatten               # => [0,1,2,3,4,5,6,7,8,9,'A','B','C','D','E','F']
octal = (binary + octal).uniq            # => [0, 1, 2, 3, 4, 5, 6, 7]
 
a = [0, 1, 2, 3, 4, 5]    # array of 6 elements
b = a.map { |x| 2**x }    # => [1, 2, 4, 8, 16, 32]

Hashes

Hash is an associative array which is a collections of Keys and it's associated Values

capitals = {                  
:karnataka  => 'Banglore'
:maharastra => 'Mumbai'
}
capitals[:westbengal] = 'Kolkata'     # append a new element
capitals[:karnataka] = 'Bengaluru'    # change an element's association

Iterators and Blocks

Iterators

alias chant print
108.times {chant 'maRa'}    # see the change for yourself

Blocks

def iterator
        yield 'yield, '
        yield 'blocks,'
        yield 'Ruby'
end
iterator {|yeilded| print "use #{yeilded}"}    # outputs, use yield, use blocks, use Ruby

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Ruby 1.9.2 Version is used for the examples on Win Intel x86 / Linux AMD64 Platforms

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