Walrus Operator

The Walrus operator allows you to perform assignment expresssions, where the second operand to your assignment is the value of the expression.

Examples

if a := get_value() then
    -- 'a' was assigned a truthy value.
else
    -- 'a' was assigned a falsy value.
end

--> This code is semantically equal.
local a = get_value()
if a then
    -- 'a' was assigned a truthy value.
else
    -- 'a' was assigned a falsy value.
end

Expressions for the Walrus operator may be evaluated multiple times in circumstances like loops.

local function get()
    return true
end

while a := get() do
    --> This will loop forever. It'll keep evaluating `a := get()`, just like any other condition.
end

Like any other expression, you can also do things like this:

if (a := math.random(1, 10)) < 5 then
    print("A is less than five! Value: " .. a)
else
    print("A is greater than five! Value: " .. a)
end

The Walrus operator can be used anywhere an expression is accepted.
The Walrus operator does not support tuple assignment.

This feature is inspired from Python's implementation, which can be found here.

Examples​

Examples