5.1.16. Modules and Program Structure

This tutorial covers the file layout (options, module, require), creating and using a separate module file, public vs private visibility, qualified calls with ::, and common standard library modules.

5.1.16.1. File layout

A typical daslang file follows this order:

options gen2                         // compiler options
module my_module public              // module declaration
require math                         // imports
// ... declarations (struct, enum, def, etc.)

The module line must appear before any declarations.

5.1.16.2. Module declaration

The module keyword names the current file. Omit it to default to the filename:

module my_lib public      // public declarations by default
module my_lib private     // private declarations by default
module my_lib shared      // shared across contexts

5.1.16.3. Creating a module

Create a file tutorial_helpers.das next to your main script:

options gen2
module tutorial_helpers public

struct Item {
    name : string
    value : int
}

def make_item(n : string; v : int) : Item {
    return Item(name=n, value=v)
}

def describe(item : Item) : string {
    return "{item.name} (worth {item.value})"
}

def private internal_id(item : Item) : int {
    return item.value * 31
}

let MAX_ITEMS = 100

5.1.16.4. Using a module

In the main file, import and use it:

require tutorial_helpers

let sword = make_item("Sword", 150)
print("{describe(sword)}\n")
print("max: {MAX_ITEMS}\n")

If the module file is in the same directory, require finds it by name.

5.1.16.5. Qualified calls

Use module::function to disambiguate:

let shield = tutorial_helpers::make_item("Shield", 80)
let r = math::sqrt(16.0)

This is essential when two modules export the same function name.

5.1.16.6. Visibility

Each declaration can override the module default:

def public  helper() { ... }    // always visible
def private internal() { ... }  // only within this module

Private functions like internal_id() above cannot be called from other modules — the compiler reports an error.

5.1.16.7. Re-exporting

require ... public re-exports a module to your importers:

require math public       // importers of this module also get math

5.1.16.8. Common standard library modules

Module	Purpose
`math`	sin, cos, sqrt, atan2, etc.
`strings`	to_int, to_float, starts_with, etc.
`fio`	File I/O
`rtti`	Runtime type information
`daslib/json`	JSON parsing
`daslib/regex`	Regular expressions
`daslib/algorithm`	Sorting and searching
`daslib/strings_boost`	Advanced string utilities