Arrays Checkpoint

_notes

## Returning Array elements
  - fruits = ["apple", "banana", "orange"]
    - fruits.first (**Cool - there's a plain english descriptions for the position!!**)
      - #=> "apple"
    - fruits.third
      - #=> "orange"
    - fruits.last
      - #=> "orange"
      
- If we want to add an element to the end of an array we can use the "shovel" (<<) operator.
  - numbers = [1]
  - numbers << 2
  - numbers
    - #=> [1,2]
    
##Negative Indexes

Indexes, like the the ones in the examples above, retrieve elements from an array going left to right. Ruby also allows us to define negative indexes, which retrieve elements from right to left. For example:

fruits = ["apple", "banana", "orange"]

- fruits[-1]
  - #=> "orange"

- fruits[-2]
  - #=> "banana"

- fruits[-3]
  - #=> "apple"

Notice that when using negative indexes, counting starts at -1, rather than 0.

_output

```Bloc output - Array Definition
```
new_array creates an array of numbers
new_array creates an array of strings
first_and_last creates new array with numbers
first_and_last creates new array with strings

```Bloc output - Array Methods
```

reverse_plus_one creates a new array for a short array
 reverse_plus_one creates a new array for a longer array
 pluses_everywhere returns a single plus for a short array
 pluses_everywhere returns pluses for longer arrays
 array_quantity_plus_one returns the number of items for a short array plus one
 array_quantity_plus_one returns the number of items for a long array plus one
 
 ```Bloc output - Grocery List
 ```
  add_item adds an item to the end of the list
 add_item doesn't add an item if the list already has it
 remove_item removes an item if it's in the list
 remove_item removes an item if it's in the list
 remove_item doesn't remove an item if it's not in the list
 full_list returns the list sorted
 full_list returns the list sorted without duplicates
 

_questions

Just want to make sure I got this right (QUESTIONS ARE COMMENTED ON THE LINE ITSELF)

# Grocery List section

def add_item(item, list)
  if !(list.include?(item))
    list << item     # **DOES THIS EXPRESSION RETURN THE APPENDED LIST??**
  else
    list  # **IS THIS CORRECT - JUST RETURN THE LIST ITSELF?**
  end
end

def remove_item(item, list)
    list.delete(item) # **AM I CORRECT IN ASSUMING THAT list.delete(item) DOES NOT RETURN THE LIST??**
    list # **...HENCE RETURNING IT HERE??**
end

def full_list(list) #the list argument is expected to be an array of grocery items
    list.uniq.sort  # **DOES THIS EXPRESSION RETURN THE UNIQUE/SORTED LIST??**
end

Arrays Checkpoint

# ARRAY DEFINITION

def new_array(a,b,c,d)
  #return an array consiting of the arguments here
  $new_array = [a,b,c,d]
end
  
def first_and_last(a)
  $first_and_last = [a.first, a.last]
end

# Array Methods

def reverse_plus_one(a)
  a << a.first
  a.reverse
end

def pluses_everywhere(a)
  #convert the array argument to a string and insert a "+" between each element
  a.join("+")
end

def array_quantity_plus_one(a)
  # return the number of elements in the array argument, plus 1.
  a.length + 1
end

#Grocery List

# Create prog - manage grocery list

def add_item(item, list)
  if !(list.include?(item))
    list << item
  else
    list
  end
end

def remove_item(item, list)
    list.delete(item)
    list
end

def full_list(list) #the list argument is expected to be an array of grocery items
    list.uniq.sort
end

  

[1] pry(main)> x = [1,2,3]
=> [1, 2, 3]
[2] pry(main)> x.third
NoMethodError: undefined method `third' for [1, 2, 3]:Array
from (pry):2:in `__pry__'
[3] pry(main)> require 'active_support/all'
=> true
[4] pry(main)> x.third
=> 3