Modules, Imports, and the Prelude

Every source file is a module. Imports bring typed top-level bindings from another module into the current one.

Importing Names

Paths resolve relative to the importing file:

from p"helpers.dewy" import format_name
import format_name from p"helpers.dewy"

The order may be written either way. Import several names with a comma sequence or a parenthesized whitespace sequence:

from p"helpers.dewy" import parse, validate, save
from p"helpers.dewy" import (parse validate save)

Rename a binding with as:

from p"helpers.dewy" import (save as save_document)

Namespaces and Splats

Bind a module namespace when several uses should remain qualified:

import p"helpers.dewy" as helpers

let result = helpers.parse(input)
let item:helpers.Item = result

Importing only the path splats its top-level bindings into the current scope:

import p"helpers.dewy"

Name collisions and import cycles are compile errors.

Paths Are Compile-Time Values

p is an ordinary prelude function constructing a structural path value:

from [path="helpers.dewy"] import parse

The compiler must know the exact path while building the module graph. A runtime-computed string cannot choose a source import.

File suffixes are conventional; a file containing Dewy source does not acquire different language semantics because of its extension.

Initialization

Reachable modules initialize once in dependency order. Their top-level expressions run before the entry module proceeds to main.

Targets

$target is the compile-time name of the backend being compiled for (x86_64, riscv, arm, c, wasm32), the same names udewy uses. Comparing it selects code during checking, so an arm for another target is skipped entirely and may import files that exist only there:

if $target in? ["x86_64" "riscv" "arm" "c"] {
    from p"linux/io.dewy" import (_write_stdout _write_stderr)
}
if $target not =? "wasm32" { import p"native_only.dewy" }

$supported_targets = ["x86_64" "c"] rejects compilation for any other target. Only comparisons of $target fold this way; an ordinary if true still checks every arm.

The Source Prelude

Ordinary modules receive a small set of default imports: path construction, printing, rationals and fixed-point numbers, units, and host facilities such as sleep where the target supplies them. The prelude's portable files import their target-specific primitives with the same $target gating.

A module can opt out:

$no_prelude = true

That choice applies to the containing module and does not silently change modules it imports.

Provisional design: Installed package lookup, non-source artifacts, and the naming policy for domain libraries are still evolving. File-relative source imports and the per-module prelude rule are settled.

The Reference defines module resolution and initialization.