Ruby Programming Notes

Ruby Programming

This page contains some of my notes on Ruby programming... it is not intended as a 'Tutorial'
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Bases

Decimal	100 0d100
Hexadecimal	0x1FF
Binary	0b10101010
Octal	0o1234567

Operators

Operatior	Description	Example
+	Add	a + b will give 30
−	Subtract	a - b will give -10
*	Multiply	a * b will give 200
/	Divide	b / a will give 2
%	Modulus − Get Remainder	b % a will give 0
**	Exponent − Power	a**b will give 10 to the power 20
=	Simple assignment operator, assigns values from right side operands to left side operand.	c = a + b will assign the value of a + b into c
+=	Add AND assignment operator, adds right operand to the left operand and assign the result to left operand.	c += a is equivalent to c = c + a
-=	Subtract AND assignment operator, subtracts right operand from the left operand and assign the result to left operand.	c -= a is equivalent to c = c - a
*=	Multiply AND assignment operator, multiplies right operand with the left operand and assign the result to left operand.	c = a is equivalent to c = c a
/=	Divide AND assignment operator, divides left operand with the right operand and assign the result to left operand.	c /= a is equivalent to c = c / a
%=	Modulus AND assignment operator, takes modulus using two operands and assign the result to left operand.	c %= a is equivalent to c = c % a
**=	Exponent AND assignment operator, performs exponential (power) calculation on operators and assign value to the left operand.	c = a is equivalent to c = c a
=	Simple assignment operator, assigns values from right side operands to left side operand.	c = a + b will assign the value of a + b into c
+=	Add AND assignment operator, adds right operand to the left operand and assign the result to left operand.	c += a is equivalent to c = c + a
-=	Subtract AND assignment operator, subtracts right operand from the left operand and assign the result to left operand.	c -= a is equivalent to c = c - a
==	Checks if the value of two operands are equal or not, if yes then condition becomes true.	(a == b) is not true.
===	Used to test equality within a when clause of a case statement.	(1...10) === 5 returns true.
!=	Checks if the value of two operands are equal or not, if values are not equal then condition becomes true.	(a != b) is true.
>	Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.	(a > b) is not true.
<	Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.	(a < b) is true.
>=	Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true.	(a >= b) is not true.
<=	Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true.	(a <= b) is true.
<=>	Combined comparison operator. Returns 0 if first operand equals second, 1 if first operand is greater than the second and -1 if first operand is less than the second.	(a <=> b) returns -1.
.eql?	True if the receiver and argument have both the same type and equal values.	1 == 1.0 returns true, but 1.eql?(1.0) is false.
equal?	True if the receiver and argument have the same object id.	if aObj is duplicate of bObj then aObj == bObj is true, a.equal?bObj is false but a.equal?aObj is true.
=>	Hashmap literal definition	key1 => value1
&	Binary AND Operator copies a bit to the result if it exists in both operands.	(a & b) will give 12, which is 0000 1100
\|	Binary OR Operator copies a bit if it exists in either operand.	(a \| b) will give 61, which is 0011 1101
^	Binary XOR Operator copies the bit if it is set in one operand but not both.	(a ^ b) will give 49, which is 0011 0001
~	Binary Ones Complement Operator is unary and has the effect of 'flipping' bits.	(~a ) will give -61, which is 1100 0011 in 2's complement form due to a signed binary number.
<<	Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand.	a << 2 will give 240, which is 1111 0000
>>	Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand.	a >> 2 will give 15, which is 0000 1111
? :	Conditional Expression	If Condition is true ? Then value X : Otherwise value Y
..	Creates a range from start point to end point inclusive.	1..10 Creates a range from 1 to 10 inclusive.
...	Creates a range from start point to end point exclusive.	1...10 Creates a range from 1 to 9.
=~	matches a String against a regular expression, returns the position/index if found else nil	"Hello World" =~ /Wo/
!~	'Does not contain�	"Hello World" !~ /Mo/

Notes

Print Hello World	puts "Hello World!"
Print Character	putc "!"
String concatenation	str = "Billy" + " Bob"
Rem statement	# puts "don't show this"
Multiple commands on one line	test ="hello"; puts test
Comma in numbers 10,000	test =10_000;puts test
Using Quotes in strings	puts "Quote: \"!" puts %(Quote: "!)
Get user input	name=gets puts "Hello "+name
Remove a newline	name=gets.chomp
Print variable	puts "value = #{var}" puts "value = " + var v= var.to_s
Loop	for i in 0..5 puts i end
Loop	[1,2].each do \|i\| puts i end
Loop Break	for i in 0..10 if i==5 break end puts i end
Loop Next
While	i = 1 while i<=3 do puts i; i+=1 end
until	begin i+=1 end until i>4
Break while	i = 0 while true do puts i; i+= 1 break if i>5 end
If	if var<3 puts "Low" elsif var<10 puts "Mid" else puts "High" end
If Not	unless 2==1 puts 'Not True' end
case	case var when 1 puts "one" when 2..4 puts "2/3/4" else puts "something" end
function with arg	def myfunc(param = "default",param2=123t) end myfunc(1,2)
Return a value	def test return "Hello World" end def test2 "Goodbye cruel world" end puts test puts test2
set multiple objects to the same object	a=b=c
create identifier as symbol object	:name
Run a program	Load "File.rb"
NULL / Empty object	nil
INC / DEC	V+=1 V-=1
Convert object to string	to_s
convert integer to float convert string to integer	9 / 5.to_f "7".to_i
New object	A= MyObj.new
Class definition	class MyObj def initialize(name) @myname=name puts "Created "+name end end o = MyObj.new("Test")
function of the class	#in MyObj def myname return @myname end puts "My Name is "+o.myname
Local (instance var)	@var
Class Var (Shared across all instances of class)	class MyObj def initialize(name) @@myname=name puts "Created "+name end def name ; return @@myname ; end end o = MyObj.new("Test1") ; p = MyObj.new("Test2") puts o.name ; puts p.name
Module (Prevents namespace clashes)	module MyMod MyVar="Test" end puts MyMod::MyVar
Include file (for modules)	require "/sources/mymod.rb" puts MyMod::MyVar
Global var	$myglobal=1
Constant (upper case first letter	Const=1
Current object	self
Random Psuedorandom	rand srand
File load	File.open("testfile.txt") do \|f\| lines=f.readlines lines.each do \|l\| puts l end end
Substring (mid)	test="<<<Hello>>>" puts test[3...8] puts test[-3,3]
Length, Uppercase Lowercase	puts test.length puts test.upcase puts test.downcase
contains Instr	puts test =~ /llo/
Multiline string definition	str = <<TEST Line 1 Line 2 Line 3 TEST puts str
2D Array	box=Array.new(3){ Array.new(3,'-') } box[0][0]="["; box[0][2]="["; box[2][0]="]"; box[2][2]="]" for y in 0..2 for x in 0..2 ; putc box[x][y] ; end puts "" end
Paralell assignment	black,white=0,255