Modules

Why Modules?

As programs grow, you need ways to split code across files, avoid name collisions, and control what’s visible to the outside world. Zap’s module system is file-based and explicit.

Importing Modules

import std.io          // import the io module from the standard library
import std.collections // import the collections module

fn main() {
    io.println("Hello from io!")
}

Selective Imports

import std.io { println, read_line }

fn main() {
    println("What's your name?")
    let name = read_line()
}

Aliased Imports

import std.collections as col

let list = col.List.new()

Creating Your Own Modules

Every .zap file is a module. The file name is the module name:

my_project/
├── main.zap
├── math.zap
└── utils/
    ├── strings.zap
    └── files.zap

main.zap

import math
import utils.strings

fn main() {
    print(math.add(2, 3))
    print(strings.capitalize("hello"))
}

Exports

By default, all top-level declarations in a module are private. Use pub to make them accessible:

math.zap

pub fn add(a: Int, b: Int) -> Int {
    a + b
}

fn internal_helper() {
    // not visible outside this module
}

Nested Modules

Directories create module hierarchies:

utils/strings.zap

pub fn capitalize(s: String) -> String {
    // ...
}

// Access as: utils.strings.capitalize(...)

Module Conventions

Convention	Description
One module per file	Keep modules focused and small
pub only what’s needed	Minimise your public API surface
Group related modules	Use directories for logical grouping
main.zap as entry point	The compiler looks for main() here

Next Steps

Explore the Standard Library to see what modules ship with Zap.