Ruby: Symbol Review

Question 1

\

Answer 1

Escape sequence for string: Escapes the “" character.

Question 2

'

Answer 2

Escape sequence for single-quoted string. Escape the single quote character.

Question 3

"

Answer 3

Escape sequence for double-quoted string. Escape the double quote character.

Question 4

\n

Answer 4

Escape sequence for double-quoted string. Starts a new line.

Question 5

\s

Answer 5

Escape sequence for double-quoted string. Adds a space.

Question 6

\t

Answer 6

Escape sequence for double-quoted string. Adds a tabbed space (~5 spaces)

Question 7

\b

Answer 7

Escape sequence for double-quoted string. Deletes a space (backspace function). In IRB, only works with puts.

Question 8

\a

Answer 8

Escape sequence. Sends an alert to the user. The alert may be dependent on the user’s computer - it may flash, be an audio alert, etc.

Question 9

\f

Answer 9

Escape sequence. Begins a new line at the same point as the previous line ended.

example: puts “Hello\fWorld”

Hello
World
=> nil

Question 10

\v

Answer 10

Escape sequence. Begins a new line at the same point as the previous line ended.

example: puts “Hello\fWorld”

Hello
World
=> nil

Question 11

..

Answer 11

The two dot construction for a Ruby Range means INCLUSIVE of the final character.

Example:
(1..10)
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Question 12

…

Answer 12

The three dot construction for a Ruby Range means EXCLUSIVE of the final character.

Example:
(1…10)
=> [1, 2, 3, 4, 5, 6, 7, 8, 9]

Question 13

||

Answer 13

Called Logical OR Operator. If any of the two operands are non zero then then condition becomes true. Same as ‘or’ operator.

Example:

(a || b) is true.

Question 14

&&

Answer 14

Called Logical AND operator. If both the operands are non zero then then condition becomes true. Same as ‘and’ operator.

Example:

(a && b) is true.

Question 15

not

Answer 15

Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false.

Example:

not(a && b) is false.

Question 16

!

Answer 16

Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false.

Example:

!(a && b) is false.

Question 17

or

Answer 17

Called Logical OR Operator. If any of the two operands are non zero then then condition becomes true. Same as ‘||’ operator.

Example:

(a or b) is true.

Question 18

and

Answer 18

Called Logical AND operator. If both the operands are true then then condition becomes true. Same as ‘&&’ operator.

Example:

(a and b) is true.

Question 19

+

Answer 19

Addition - Adds values on either side of the operator.

Example:

a + b will give 30

Question 20

-

Answer 20

Subtraction - Subtracts right hand operand from left hand operand.

Example:

a - b will give -10

Question 21

*

Answer 21

Multiplication - Multiplies values on either side of the operator.

Example:

a * b will give 200

Question 22

/

Answer 22

Division - Divides left hand operand by right hand operand.

Example:

10 / 5 will give 2

Question 23

%

Answer 23

Modulus - Divides left hand operand by right hand operand and returns remainder.

Example:

10 % 4 will give 2

Question 24

**

Answer 24

Exponent - Performs exponential (power) calculation on operators.

Example:

6**3 will give 6 to the power 3

Question 25

==

Answer 25

Checks if the value of two operands are equal or not, if yes then condition becomes true. Example: (a == b) is not true.

Question 26

!=

Answer 26

Checks if the value of two operands are equal or not, if values are not equal then condition becomes true. Example: (a != b) is true.

Question 27

>

Answer 27

Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true. Example: (8 > 10) is not true.

Question 28

<

Answer 28

Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true. Example: (8 < 10) is true.

Question 29

>=

Answer 29

Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true. Example: (8 >= 10) is not true.

Question 30

<=

Answer 30

Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true. Example: (8 <= 10) is true.

Answer 31

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. The spaceship operator is used to make comparisons. The results are given relative to zero. Asking, which side do I belong to? LEFT OR RIGHT? Example: 1 2 will give -1 Because 1 is LESS than 2, it is -1. 2 1 will give 1 Because 2 is GREATER than 1, it is 1.

Question 32

===

Answer 32

Used to test equality within a when clause of a case statement. Example: (1...10) === 5 returns true. [Does any number in the range == 5?] true

Question 33

.eql?

Answer 33

True if the receiver and argument have both the same type and equal values. Example: 1 == 1.0 returns true, but 1.eql?(1.0) is false.

Question 34

equal?

Answer 34

True if the receiver and argument have the same object id. Example: a = 2 a.equal?(2) true

Question 35

=

Answer 35

Simple assignment operator, Assigns values from right side operands to left side operand. Example: c = a + b will assign value of a + b into c

Question 36

+=

Answer 36

Add AND assignment operator, It adds right operand to the left operand and assign the result to left operand. Example: c += a is equivalent to c = c + a

Question 37

-=

Answer 37

Subtract AND assignment operator, It subtracts right operand from the left operand and assign the result to left operand. Example: c -= a is equivalent to c = c - a

Question 38

*=

Answer 38

Multiply AND assignment operator, It multiplies right operand with the left operand and assign the result to left operand. Example: c *= a is equivalent to c = c * a

Question 39

/=

Answer 39

Divide AND assignment operator, It divides left operand with the right operand and assign the result to left operand. Example: c /= a is equivalent to c = c / a

Question 40

%=

Answer 40

Modulus AND assignment operator, It takes modulus using two operands and assign the result to left operand. Example: c %= a is equivalent to c = c % a Further Explanation: a = 10 a % 4 => 2 if you all the variable "a" again, it will be still be 10, because it wasn't assigned. However, if you use: a %= 4 => 2 Then a has been set to 2.

Question 41

**=

Answer 41

Exponent AND assignment operator, Performs exponential (power) calculation on operators and assign value to the left operand. Example: c **= a is equivalent to c = c ** a

Question 42

defined?

Answer 42

defined? is a special operator that takes the form of a method call to determine whether or not the passed expression is defined. It returns a description string of the expression, or nil if the expression isn't defined. Example: foo = 42 defined? foo # => "local-variable" defined? $_ # => "global-variable" defined? bar # => nil (undefined) defined? method_call # True if a method is defined defined? puts # => "method" defined? puts(bar) # => nil (bar is not defined here) defined? unpack # => nil (not defined here)

Question 43

? :

Answer 43

Ternary Operator; conditional. If Condition is true ? Then value X : Otherwise value Y if a == b ? "a":"b"

Question 44

alias

Answer 44

Alias renames and duplicates (gives an alias to), but not replaces, a method name. Example: class User def full_name puts "Johnnie Walker" end alias name full_name end User.new.name #=>Johnnie Walker

Question 45

[ ]

Answer 45

Symbol for an array.

Question 46

::

Answer 46

The :: symbol is used to access variables that belong to a module. For example: ``` module ExampleModule tangerine = "orange-like fruit" ``` then on another sheet we require that. require '.examplemodule' ExampleModule::tangerine ^ to call variable

Question 47

Add-on modifiers (with if statements)

Answer 47

Ruby Statement modifiers let you tack conditional statements onto the end of a normal statement: Examples: mon, day, year = $1, $2, $3 if date =~ /(\d\d)-(\d\d)-(\d\d)/ puts "a = #{a}" if $DEBUG print total unless total.zero?

Question 48

Toggle-style (adding modifiers after the 'end')

Answer 48

Example: if artist == "John Coltrane" artist = "'Trane" end unless use_nicknames == "no"

Question 49

Case Expressions

Answer 49

2 types of case: the first, similar to a series of if statements, the second, you specify a target at the top of the case: Example 1: ``` case when song.name == "Misty" puts "Not again!" when song.duration > 120 puts "Too long!" when Time.now.hour > 21 puts "It's too late" else song.play end ``` Example 2: ``` case command when "debug" dump_debug_info dump_symbols when /p\s+(\w+)/ dump_variable($1) when "quit", "exit" exit else print "Illegal command: #{command}" end ```

Question 50

Case Statements Using Then syntax

Answer 50

``` kind = case year when 1850..1889 then "Blues" when 1890..1909 then "Ragtime" when 1910..1929 then "New Orleans Jazz" when 1930..1939 then "Swing" when 1940..1950 then "Bebop" else "Jazz" end ```