Introduction Flashcards
1
Q
single line comment
A
comment
2
Q
single line comment
A
comment
3
Q
multi-line comment
A
=begin this is a multi line comment =end
4
Q
Boolean
A
true or false
5
Q
string
A
“just text”
6
Q
A
prints a value in the console
7
Q
puts
A
prints a value but adds a line break
8
Q
methods
A
a “skill” or feature of an objec
9
Q
.length
A
shows the length of characters in a string
10
Q
.reverse
A
reverses a string
11
Q
.upcase
A
capitalises an entire string
12
Q
.downcase
A
converts a string to all lowercase
13
Q
gets
A
retrieves user input
14
Q
.chomp
A
removes a blank line
15
Q
{variable}
A
retrieves variable data (user input) and inserts in a string
16
Q
if
A
evaluates something to true or false
17
Q
elsif
A
to insert another evaluations after an “if”
18
Q
else
A
evaluates everything else if the first “if” or “elsif” are false
19
Q
comparator
A
a sign that compares to values such as
== “is equal to”
< is less than
20
Q
A
less than
21
Q
>
A
greater than
22
Q
<=
A
less than or equal to
23
Q
> =
A
greater than or equal to
24
Q
!=
A
not equal to
25
==
equal to
26
&&
and
27
||
or
28
!
not. reverses a true to false object to be the opposite
29
unless
an unless function, another version of "if"
runs a function unless the following is true
30
.gsub
substitutes a letter in a string ie
user_input.gsub (/s/, "th")
the string "th" is what replaces every s
31
end
ends a if, else function
32
multi-line comment
```
=begin
this is
a
multi line
comment
=end
```
33
Boolean
true or false
34
string
"just text"
35
print
prints a value in the console
36
puts
prints a value but adds a line break
37
methods
a "skill" or feature of an objec
38
.length
shows the length of characters in a string
39
.reverse
reverses a string
40
.upcase
capitalises an entire string
41
.downcase
converts a string to all lowercase
42
gets
retrieves user input
43
.chomp
removes a blank line
44
#{variable}
String interpolation. retrieves variable data (user input) and inserts in a string
45
if
evaluates something to true or false
46
elsif
to insert another evaluations after an "if"
47
else
evaluates everything else if the first "if" or "elsif" are false
48
comparator
a sign that compares to values such as
== "is equal to"
< is less than
49
less than
50
>
greater than
51
<=
less than or equal to
52
>=
greater than or equal to
53
!=
not equal to
54
==
equal to
55
&&
and
56
||
or
57
!
not. reverses a true to false object to be the opposite
58
unless
an unless function. an action runs unless a condition is true
59
.gsub
substitutes a letter in a string ie
user_input.gsub (/s/, "th")
the string "th" is what replaces every s
60
end
ends a if, else function
61
one-line If statement
an if statement can be written without and "end" if on one line
syntax
expression if boolean
ex.
puts "hello" if true
-> hello
62
one-line unless statment
no need for end
i.e.
puts "hello" unless 2*3 == 5
-> hello
63
ternary expression
a substitute for an if else statement. it takes three arguments: a boolean, an expression to evaluate if the boolean is true, and an expression to evaluate if the boolean is false.
syntax
boolean ? Do this if true: Do this if false
i.e.
puts 3 < 4 ? "3 is less than 4!" : "3 is not less than 4."
64
| | =
conditional assignment operator. assigns a real value to a variable only when its current value is false of nil. Otherwise ruby keeps its original value
i.e.
boyfriend = nil
boyfriend ||= "Jimmy Jr."
boyfriend ||= "Josh"
```
puts boyfriend
# => "Jimmy Jr."
```
65
short circuit evuation
for boolean operators && or ||, ruby will only evaluate to the point it is sure whether the statement is true or false.
66
.upto
iterates over values in a specific range upwards
```
i.e.
"B".upto("F") { |letter| print letter, " " }
# => B C D E F
```
67
.downto
iterates over values in a specific range downwards
i.e
5.downto(0) { |num| print num, " " }
# => 5 4 3 2 1 0
68
.respond_to?
takes a symbol representing a method name and returns true if that method can be called on the object and false otherwise.
```
puts "A".respond_to?(:push)
# => false
# Here, the following Ruby code will return false since .push can’t be called on a String object.
```
```
puts "A".respond_to?(:next)
# => true
# Here, however, the following Ruby code will return true since .next can be called on a String object. Calling .next on the letter “A” would return the letter “”.
```
69
<
concatenation operator. an alternative to push. can be used to add an element to the end of an array or a string
array = [1, 2, 3]
array << 4
print array
#Output => [1, 2, 3, 4]
```
puts "Hello," << " welcome to Codecademy."
#Output => Hello, welcome to Codecademy.
```
