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Compile-Time Evaluation

Pluto's parser provides some powerful constructs which allow you to write code that will never be seen at runtime.

Function calls​

Certain standard library functions can be called at compile-time, as long as the arguments are also known at compile-time, by using the "$" symbol before the function call.

pluto
local runtime = require("crypto").joaat("Hello, World!")
local compile = $crypto.joaat("Hello, World!")
assert(runtime == compile)

If you're unfamiliar with compile-time evaluation, this is essentially what the code turns into:

pluto
local runtime = require("crypto").joaat("Hello, World!")
local compile = 847757641 -- The JOAAT hash of "Hello, World!"
assert(runtime == compile)

This is available on preloaded Pluto libraries, such as:

  • base32
  • base58
  • base64
  • crypto
  • json
  • url

And on the following functions:

  • io.contents
  • tostring
  • utostring
  • tonumber
  • utonumber
  • type

Variables​

Compile-time constant variables can be defined via the $define statement:

pluto
$define a = 123

This may seem identical to a local declared with the const attribute:

pluto
local a <const> = 123

However, $define also enforces that the assigned variable is a compile-time constant:

pluto
local a <const> = {}
$define a = {} -- Error: variable was not assigned a compile-time constant value

Conditionals​

If there is certain code you only want to have compiled in for a certain build, such as a debug build, you can use compile-time conditionals:

pluto
$define DEBUG = true
$if DEBUG then
    print("Script running in debug mode")
$else
    print("Script running in release mode")
$end

In this case, only one of the two paths will be compiled in; the rest will not take up any space.