Scope

A scope is like a dictionary with entries inside, where keys hold values.

Definition

Scopes are defined with curly brackets {}, like so:

myCoolScope = {
  place = 'here'
  when = 'now'
}

Scopes store entries in alphabetical order. This becomes evident when you map over a scope.

There are three ways you can directly access entries inside a scope.

myCoolScope.place  # output: 'here'

# assuming prop = 'place' 
myCoolScope(prop)  # output: 'here'

Either way, if the property is not present, null is returned. And if the outer scope is not found in scope, an error is raised.

You can chain the missing outer by using question-dot ?. operator:

nonExisting?.prop  # null

The optional chaining won't raise an error when the outer scope is null.

logical AND/OR evaluate empty scopes as false, otherwise true

The second operand works as if it were a patch for the first operand:

x = { a = 1, b = 3 }
y = { b = 2 }

x + y  # { a = 1, b = 2 }
y + x  # { a = 1, b = 3 }

values from second operand replace values from the first operand

The subtraction operation results in removing the elements from the second operand that are also present in the first operand:

x = { a = 1, b = 3 }
y = { a = 1 }

x - y  # { b = 3 }

only values that are exactly identical are removed