Modules in Sesi

Modules let you split code across .sesi files and reuse it. Use export to expose values from a file and import or allow to bring them in.

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Exporting

Mark any let binding or fn declaration with export to make it available to other files:

// math.sesi
export fn add(a, b) { return a + b }
export fn multiply(a, b) { return a * b }
export let PI = 3.14159

Only exported names are visible to importers. Everything else stays private to the file.

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Importing — import

Pull named exports directly into the current scope:

import {
  add,
  multiply,
  PI
} from "math"

show add(10, 20)   // 30
show PI            // 3.14159

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Importing — allow

allow is Sesi's scoped import syntax. It has two forms:

Named bindings

Import specific exports directly into scope:

allow "math" in with {
  add, multiply
}

show add(3, 4)   // 7

Namespace object

Import the entire module under a single identifier:

allow "math" in as Math

show Math.add(3, 4)      // 7
show Math.multiply(2, 5) // 10

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Standard Library Modules

Sesi ships with built-in standard library modules:

... and more!

allow "std/math" in as Math
allow "std/time" in as Time
allow "std/game" in as Game

show Math.PI
show Math.atan2(1, 0)
show Math.min(8, 3, 5)
show Math.floor(3.9) // floor is globally available too
show Time.now()

std/math provides the complete stable JavaScript Math surface supported by Node.js 20+.

std/game requires npm install @misterscan/sesi-game and local mode (sesi -l). Its complete API is in GAME.md.

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Module Resolution Order

When you import "mymodule", Sesi searches for mymodule.sesi (or the folder mymodule for directory modules) in this order:

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Third-Party Package Management

Sesi features a built-in, git-centric package manager to install and share reusable libraries. Packages are stored inside a local sesi_modules directory in your project.

Project Manifest (sesi.json)

To track dependencies, Sesi uses a simple sesi.json file in the root of your project:

{
  "name": "my-project",
  "version": "1.0.0",
  "dependencies": {
    "http-router": "example-repo/http-router#v1.0.0"
  }
}

Installation Commands

• Install a specific package:

bash

sesi install owner/repo#ref

This downloads the package from GitHub, extracts it to sesi_modules/repo, and registers it inside sesi.json. You can specify branch names, tag names, or commit hashes using #ref.

• Restore all dependencies:

bash

sesi install

This reads your sesi.json and restores all dependencies into sesi_modules/.

Directory Modules & Entry Points

When you import a third-party package folder (e.g. allow "repo" in as Repo), Sesi automatically resolves the module's entry point. It checks the directory for:

1. sesi_modules/<package-name>/index.sesi
2. sesi_modules/<package-name>/main.sesi

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Global Library (~/.sesi/lib)

Copy a module to the global library to make it importable from any project on your system:

# macOS / Unix
cp mymodule.sesi ~/.sesi/lib/

# Windows
copy mymodule.sesi $env:USERPROFILE\.sesi\lib\

// Now importable from anywhere
allow "mymodule" in with { helper, util }

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Custom Paths (SESI_PATH)

Point SESI_PATH to additional directories for team or monorepo setups:

# macOS / Unix
export SESI_PATH="/mylibs/shared:/projects/common"

# Windows
$env:SESI_PATH = "C:\MyLibs\shared;C:\Projects\common"

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Quick Reference

// Export
export fn greet(name) { show "Hello," name }
export let VERSION = "1.9.0"

// import (named)
import { greet, VERSION } from "mymodule"

// allow (named bindings)
allow "mymodule" in with { greet, VERSION }

// allow (namespace)
allow "mymodule" in as Mod
Mod.greet("Ada")

// Standard library
allow "std/math" in as Math
allow "std/time" in as Time

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