Week 1 Diagnostic

Floats and Integers

What’s the difference between a float and integer? Floats have decimal places and Integers are whole numbers
Float example 1.55
Integer example 1

What’s are the similarities and differences between BigNum and FixNum?
They are whole numbers and they are within the same level

What will 4.0 / 2 return?
2.0

What will 1.5.to_i.to_f return?
1.0

What part of this expression ("hi" * 5?) is “syntactic sugar”? What does that mean?
* is the multiplication. The algorithm that do this is compex and a lot more lines but is represented by just *
? is a conditional(true or false). The algorithm is complex and a lot of lines but is represented by just ?

What will 10 % 3 return?
1

What will 5 == 10/2 return?
true

How can you write 5 to the 2nd power?
5**2

Strings

How can you grab the substring “ell” from “hello”?
String[1..3]

Give an example of string concatenation and string interpolation.
"Hello" + " " +"World"
a = "Hello"
b = "World"
puts "Here it is: #{a} #{b}"

Give examples of three variable names: a “valid name” (it will work) that goes against Ruby style, an “invalid” name (it will trigger an error), and a valid and stylistically conventional name.
tHrEe_BlInD_mIcE
3blind_mice
three_blind_mice

Arrays

How do you add to an array?
<<
.push

What will [1,2,3].shuffle do?
shuffle the order of the items in the array

What do shift and unshift do?
shift puts in an item into the an array
unshift takes an itme out of an array

Name 3 ways to retrieve 4 from this array: [4,3,5]
[0]
.pop
.shift


How would you print each word from this list (["hello", "goodbye", "cactus"]) to terminal within this output:
The word is "hello".
print "The word is " arr[0]

The word is "goodbye".
print "The word is " arr[1]

The word is "cactus".
print "The word is " arr[2]

arr.map { |word| puts "The word is "#{word} }


Flow control

What’s the difference between a while and until loop?
while loop will continue to loop while the condition set is met. It hits true or false
Until loop will continue to loop until the condtion is met. It hits true

How do you escape a pry in the middle of a loop?
!!!

Enumerables (.each)

What is the purpose of an enumerable?
To make coding easier by not having to type out every method by hand

What are the two different ways that you can represent a block?
short hand for blocks that do only one thing
arr.each { |x| #do something }

long hand for blocks that do more
arr.each do |x|
#do something
#do something else
end

Given this array ["Beth", "Lauren", "Ilana"]. How would you create a new array of just the first initials of each name?
arr.map { |initial| initial[0] }

Classes and instance methods

When you’re defining a class, how do you store attributes?
class Class
  initalize(att_1, att_2)
  end
end

What is the difference between attr_readers, attr_writers, and attr_accessors? What do each do?
attr_reader = read only
attr_writer = write only
attr_accessor = read and write

What method corresponds with .new when you create a new instance of a class?
initialize

Methods, arguments and scopes

Describe the scope that methods create. Are variables created in that scope accessible elsewhere?
Method scope create local variables that are not accessable to the class

What does the method scope have access to?
Method scope has access to sibling methods (other methods with in the same class)