Module System

Modules are loaded when their import statement runs, and each module is evaluated once.

Loading and caching

The first import of a module loads and evaluates it; later imports of the same module — including imports of individual keys, and imports from other files — reuse the cached value. Top-level side effects in a module therefore happen exactly once.

import std:println
import std:random

# The import above loaded std:random once; both calls use that same module
println(random:integer(1, 10))
println(random:integer(1, 10))

A local module that prints while loading shows this clearly. Given lib/util.si:

import std:println

println("loading lib/util")

export {
    value: 1,
}

importing it twice from the same file still prints once:

import std:println
import lib:util
import lib:util:value

println(value)
# loading lib/util
# 1

Directory modules are maps

Importing a directory produces a map-like module where keys correspond to contained .si files (and subdirectories) by basename.

See: Module Resolution