Numbers_and_Strings.md

Numbers and Strings

Table of Contents

• Numbers
• String
• Objects and Expressions

Variable data type is automatically determined by Ruby. They only need to be assigned some value before using it elsewhere

Numbers

• Integer examples
• see documentation links at end of this section for details on operators/methods for respective data types

>> num1 = 7
=> 7
>> num2 = 42
=> 42
>> total = num1 + num2
=> 49
>> puts total
49
=> nil

# no limit to integer precision, only limited by available memory
>> 34 ** 32
=> 10170102859315411774579628461341138023025901305856

>> 9 / 5
=> 1

>> 9 % 5
=> 4

• Floating point examples

>> 9.0 / 5
=> 1.8

>> area = 42.16
=> 42.16
>> area + 100
=> 142.16

• the E scientific notation can be used as well

>> sci_num1 = 3.982e5
=> 398200.0
>> sci_num2 = 9.32e-1
=> 0.932
>> sci_num1 + sci_num2
=> 398200.932

>> 2.13e21 + 5.23e22
=> 5.443e+22

• Binary numbers are prefixed with 0b or 0B (i.e digit 0 followed by lower/upper case letter b)
• Similarly, Hexadecimal numbers are prefixed with 0x or 0X
• Octal numbers are prefixed with 0. Can also use 0o or 0O (i.e digit 0 followed by lower/upper case letter o)

>> bin_num = 0b101
=> 5
>> oct_num = 0o12
=> 10
>> oct_num = 012
=> 10
>> hex_num = 0xF
=> 15

>> oct_num + hex_num
=> 25

• _ can be used for readability
  • but not at start of number and not more than one consecutively

>> 1_000_000
=> 1000000

>> 1_000.3_352
=> 1000.3352

>> 0xdead_beef
=> 3735928559

Further Reading

• ruby-doc: Integer
• ruby-doc: Float
• ruby-doc: Numeric
• ruby-doc: BigDecimal
• ruby-doc: Complex
• ruby-doc: Rational

String

• single quoted strings
• no interpolation or escape sequences
  • except for allowing \' when single quote itself is needed

>> greeting = 'Hello World'
=> "Hello World"

>> colors = 'Blue\nRed\nGreen'
=> "Blue\\nRed\\nGreen"
>> puts colors
Blue\nRed\nGreen
=> nil

>> msg = 'It\'s so good'
=> "It's so good"
>> puts msg
It's so good
=> nil

• double quoted strings
• allows escape sequences like \n for newline, \t for tab, etc
• allows interpolation when an expression is embedded inside #{}

>> colors = "Blue\nRed\nGreen"
=> "Blue\nRed\nGreen"
>> puts colors
Blue
Red
Green
=> nil

>> str1 = 'Hello'
=> "Hello"
>> msg = "#{str1} there"
=> "Hello there"

>> c = 5
=> 5
>> "I want #{c} apples and #{c*2} mangoes"
=> "I want 5 apples and 10 mangoes"

• String concatenation and repetition

>> str1 = 'Hello'
=> "Hello"
>> str2 = ' World'
=> " World"
>> str1 + str2
=> "Hello World"

# in-place concatenation
>> str1 << str2
=> "Hello World"

>> fmt = '-' * 27
=> "---------------------------"
>> puts "#{fmt}\n\t#{str1}\n#{fmt}"
---------------------------
        Hello World
---------------------------
=> nil

• Percent strings allow different delimiters than ' and " for representing strings

If you are using “(”, “[”, “{”, “<” you must close it with “)”, “]”, “}”, “>” respectively. You may use most other non-alphanumeric characters for percent string delimiters such as “%”, “|”, “^”, etc

# %q for single quoted strings
>> msg = %q(It's so good)
=> "It's so good"

# %Q for double quoted strings
>> f1 = 'mango'
=> "mango"
>> f2 = 'orange'
=> "orange"
>> puts %Q/I like "#{f1}" and "#{f2}"/
I like "mango" and "orange"
=> nil

Further Reading

• ruby-doc: strings
• ruby-doc: Percent Strings
• ruby-doc: List of Escape Sequences and more info on strings

Objects and Expressions

• Everything in Ruby is an object

>> 42.class
=> Integer

>> 3.2e3.class
=> Float

>> 'hello'.class
=> String

>> foo = [1, 4]
=> [1, 4]
>> foo.class
=> Array

>> nil.class
=> NilClass

• Use help within irb to get documentation for a method(assumes Ruby Docs is installed)
  • ex: help 'Integer.lcm' for ruby-doc: Integer.lcm

>> Integer.sqrt(25)
=> 5
>> 2.lcm(3)
=> 6
>> 64.gcd(36)
=> 4

>> 'hello'.upcase
=> "HELLO"

• Everything in Ruby is an expression

# num1 is assigned 5
# return value of this expression is 5
>> num1 = 5
=> 5

# return value of 'num1 = 42' is 42
# so num2 also is assigned the value 42
>> num2 = num1 = 42
=> 42
>> num1
=> 42
>> num2
=> 42

# return value of puts is always nil value
>> a = puts('hi')
hi
=> nil
>> a
=> nil

• Unlike Python, strings in Ruby are mutable

# in-place changing either str1 or str2 will affect the other
>> str2 = str1 = 'hello'
=> "hello"
>> str1.object_id
=> 47109181848080
>> str2.object_id
=> 47109181848080
>> str1 << ' there'
=> "hello there"
>> str2
=> "hello there"

# reassigning won't change the other
>> str1 = 'foo'
=> "foo"
>> str2
=> "hello there"

Further Reading

• Official Ruby FAQ
• ruby-doc: Object
• wikipedia: Object-oriented programming