Ruby Notes: First Checkpoints

Ruby lessons on syntax

The Difference between p and PUTS = Puts results in the value output as a string, whereas p simply outputs the true value of the object

Variables must start with lower case letter: 
my_string_variable = "hello world"
p my_string_variable 

will print out

hello world


when running a Boolean
my_boolean = true
p my_boolean 
will output
true

You can use commans to define more than one item : a, b = 1, 2
would assign a=1 and b=2

Symbols are like strings, only with less functionality. A Symbol is designated with a colon (:) to the left of a word. Symbols can contain any alpha-numeric character, but they must start with a letter

For example
p :lowdown123  (starts with letter after colon

using underscores such as this my_variable is called SNAKECASE

using various uppercases such as myOldApple is called CAMELCASE

Does normal math operations, ** = exponents (example: 2 ** 3 = 8)

You can assign math variables as numbers: for example

x = 20
p x
x = x + 5
p x  will output 25


when comparing to numbers you can use > or < for a boolean return of True False
but for equals, you have to use double equals ( 5 == 5)

You can use variables in math operations such as

jose = 37
melissa = 38
melissa > jose = true


Personal note:  If I wanted to get a users name inserted into a greeting I would od the following:

set the variable (name = "Jose")
Then I could print out a greeting with that name such as 
p "hello " + name which would result in hello Jose



DRY = Dont repeat yourself

for example

num1 = 3
num2 = 3
p "#{num1} + #{num2} = #{num1 + num2}"

is easier than


18003384752 - tg.org for student loans for judy


Cool formula

# principal amount
p = 132_000

# annual rate of interest
r = 0.0541

# number of years
t = 10

# number of times it is compounded
n = 12

# amount accumulated
a = p * (1 + r/n) ** (n*t)

p "After #{t} years, Law school will have cost you an unreasonable #{a} dollars "

this would be great for the site: A calculator for parents to see how much it will cost them


the Pound# Sign is a comment line
the underscore _ replaces other items you cant use in code for readbility, such as a comma


NIL  finanlly im going to get this

Square brackets ([]) are used in Ruby to reference locations. so if I ask p "Jose"[4], i wil get "s" for the output. It is trying to find the 4 character in the string which includes the quotes. Now if I tried "Jose"[7] I would get a nil because it doesnt exist.

Methods: Rather than reapat lines of code, you can call a method you defined instead. By calling the method you can make the line reperform its task. 
```
CALL = is to execute the line
Define = defines the method itself, to compose or write a method.
```
to define a method, you must do the following
```
def hello
  "Hello world"
end```

it must start with def to define it, and end with end to end it

In the above forumla, the word hello is the method name. If I run it after adding ```p hello``` i will get out ```Hello World```

def hello2
  a = 1
  b = 2
  a + b
end

this one is cool, because it will excute the last line as the output when you ```p hello2```





num1 = 3
num2 = 3
p "3 + 4 = #{num1 + num2}"