Variables

Variables hold values. You assign them with =:

x = 10
name = "alice"

Variable names must start with a letter and can contain letters, digits, and underscores.

Variables do not need to be declared before use. The first time you assign to a name, the variable is created. Use %name to explicitly declare a variable with value 0:

%counter
write(counter)     : 0
counter = 10
write(counter)     : 10

If you use a variable that has not been assigned yet, its value defaults to 0:

write(z)

In Python, an undefined variable raises NameError. In lil, you get 0. This is useful for counters and accumulators that start at zero implicitly.

Counting up works naturally:

count = 0
count = count + 1
count = count + 1
write(count)

You can reassign variables to values of any type:

x = 42
x = "now im a string"
x = 99

Assignment always goes variable = expression:

y = x + 50

Assign a number to a variable:

n = 10
write("number:", n)

Store the result of a math expression:

area = 3.14 * 5 * 5
write("area is", area)

Forcing variable types

force locks a variable completely. Once forced, you cannot change it with stringify, intify, toggle, or regular assignment:

x = 42
force x
x = 30        : ERROR: cannot assign to a forced variable
stringify x   : ERROR: cannot stringify a forced variable
unforce x     : unlock it
x = 30        : works again

Combined assignment and force:

force x = 42
unforce x = 56

unforce unlocks the variable so it can be changed again.

force with read() reads input and forces the variable to a specific type:

age = read("Enter your age: ")
intify age
force age
write("next year you will be", age + 1)

For string input with force:

name = read("Enter your name: ")
force name
write("hello", name)

Input validation without force

Use read() with intify to validate the input type without forcing the variable:

x = read("Enter a number: ")
intify x
x = "now im a string"     : allowed (not forced)
y = read("Enter text: ")
y = 42                     : allowed (not forced)

intify errors if the value is not a valid number. read() always returns a string.

Live Bindings

A live binding links one variable to another so that reads of the bound variable always reflect the current value of its source:

y = 1
live x = y
y = 42
write(x)     : prints 42

After live x = y, every read of x follows the link back to y and returns whatever y currently holds. You do not need to reassign x when y changes.

Assigning directly to x overwrites the binding and clears the live link. For a one-time copy, use plain assignment (x = y).

Changing the undefined default

By default, reading an undefined variable returns 0. Use ?default = value to change this:

?default = "Undefined"
write(someVar)     : prints "Undefined"

?default = 0
write(anotherVar)  : prints 0

The name after ? is descriptive only and is ignored by the runtime. Only one value is stored globally. Once set, all undefined variables will return that value until changed.