Acquis 23 - Do Expressions

Do expressions are do/end blocks that evaluate to the value returned through the provide keyword.

Basic usage#

Do expressions can be used anywhere an expression is allowed. The expression will be evaluated to the value returned through the provide keyword.

local x = do
    local y = 10
    provide y
end
assert(x == 10)

local z = 5 + do provide 10 end
assert(z == 15)

print(do provide local foo = "bar" provide "hello from " .. foo end) -- prints "hello from bar"

If no value is provided through the provide keyword, the do expression will evaluate to nil.

local x = do
    local y = 10
end
assert(x == nil)

Multiple values can be provided, which will fill any local variables in order.

local x, y = do
    provide 10, 20
end
assert(x == 10 and y == 20)

Catch expressions#

Do expressions naturally integrate with the catch expression and serve as a more performant pcall-like construct.

local ok, x = catch do
    provide 10
end
assert(ok and x == 10)

Use with group statements#

Do expressions can be used with group local variables to initialize them.

local x <group> = do
    local y <group> = { a = 1, b = 2 }
    provide y
end
assert(x.a == 1 and x.b == 2)