Modules

Load built-ins and your own `.rn` files with `benutzen`. Every top-level binding is exported: no export keyword.

Rain has two kinds of modules: **built-ins** (math, http, csv, …) and **user modules** (any .rn file on disk).

Load either kind with benutzen "…";. That creates a global whose name is the module stem. Then call into it with ::.

User modules have no special syntax. Write a normal .rn file: top-level var, fun, and class declarations become exports automatically. There is no export keyword and no private-by-default. If it is defined at the top level while the file loads, it is part of the module.

Paths are relative to the **current working directory** when you run ./rain script.rn. Run from the project root so benutzen "lib/model.rn" resolves correctly.

lib/greet.rn

var PREFIX = "hello";

fun forUser(name) {
  return PREFIX + ", " + name;
}

main.rn

benutzen "lib/greet.rn";

print greet::forUser("world");
print greet::PREFIX;

output

hello, world
hello

server.rn

benutzen "http";
benutzen "str";
benutzen "lib/config.rn";
benutzen "middleware/logger.rn";
benutzen "routes/register.rn";

http::cors(true);
http::use(logger::logger);
register::registerRoutes();

print str::format("server starting on port {0}", config::PORT);
http::listen(config::PORT);

routes/predict.rn

benutzen "http";
benutzen "json";
benutzen "str";
benutzen "lib/model.rn";

fun predictHandler(req) {
  var data = json::parse(req.body);
  var digit = model::predict(data.pixels);
  return http::jsonResponse(200, "{"digit": " + str::format("{0}", digit) + "}");
}

Symbol	Description	Example
`benutzen "math"`	Load a built-in module into global `math`	`benutzen "math"; print math::sqrt(9);`
`benutzen "lib/util.rn"`	Load a file; global name is the file stem (`util`)	`benutzen "lib/util.rn"; print util::helper();`
`module::name()`	Call an exported function on a loaded module	`benutzen "math"; print math::sqrt(16);`
`module::CONST`	Read an exported variable or constant	`benutzen "lib/config.rn"; print config::PORT;`

Symbol	Description	Example
`"routes/predict.rn" → predict`	Directory prefix is ignored; only the filename stem matters	`benutzen "routes/predict.rn"; predict::predictHandler(req);`
`"lib/model.rn" → model`	Nested folders are fine: stem is still just the filename	`benutzen "lib/model.rn"; model::predict(pixels);`
`"math" → math`	Built-ins use a bare name (no `.rn` suffix)	`benutzen "math"; math::zeros(2, 3);`

Symbol	Description	Example
`var x = …`	Top-level variables are exported as `module::x`	`var PORT = 8080;`
`fun name() { … }`	Top-level functions are exported as `module::name()`	`fun predict(pixels) { … }`
`class Foo { … }`	Top-level classes are exported as `module::Foo`	`class Point { … }`
`Top-level code`	Runs once on first import (I/O, setup, loading weights)	`print "loading weights...";`
`Locals inside fun`	Not exported: only top-level bindings become module fields	`fun f() { var x = 1; }`

Symbol	Description	Example
`math`	Scalars, arrays, matrices, activations, ML helpers	`benutzen "math";`
`csv`	Read CSV into arrays or matrices	`benutzen "csv";`
`str`	String search, slice, split, join, format	`benutzen "str";`
`json`	parse / stringify / keys	`benutzen "json";`
`http`	Server and HTTP client	`benutzen "http";`
`db`	SQLite	`benutzen "db";`
`io`	Files and stdin	`benutzen "io";`
`os`	Platform, env, sleep	`benutzen "os";`
`time`	Dates and clocks	`benutzen "time";`

Modules

Define a user module

Import and call it

Multi-file HTTP server

Route module (handler export)

Importing

How names are chosen

What gets exported

Built-in modules

Notes