Scope Notes Day 1

Question 1

what is lexical scope?

Answer 1

lexical scope describes how variable names resolve if we put them in structures like methods, conditionals, or blocks.

Question 2

What is local scope?

Answer 2

local scope is where you can reference variables only defined within the same scope.

def say_hello
    message = "hello"
end

say_hello
p message # NameError: undefined local variable

Question 3

what is global scope?

Answer 3

global scope is where we can define variables that are allowed to be referenced everywhere in our code regardless of local scope. Denoted using ($) “hello globe”

Question 4

what is a constant?

Answer 4

it’s another way to declare a variable to be in the global scope. A constant is denoted syntactically by beginning the name with a capital letter. By convention we like to make the entire name capital to emphasize it being a special constant.A constant variable cannot be reassigned:
FOOD = “pho”
p FOOD # => “pho”

FOOD = "ramen"  #warning: already initialized constant 
               #warning: previous definition of FOOD was here

you can still mutate that constant name without warning:
FOOD = “pho”
FOOD[0] = “P”
p FOOD # => “Pho

Question 5

what does not have its own scope?

Answer 5

Blocks don’t have their own scope, they are really a part of the containing method’s scope. Other structures like conditionals or while loops also don’t have their own scope, they are really part of the containing scope.