ava/notes/namespaces.md

Namespaces

Namespaces are the primary organizational unit of Ava. Every Ava file must define a namespace. The namespace is ALWAYS the first line of the file.

Syntax

Each namespace is an ordered, delimited, list of names. Each name is separated by the . character.

namespace foo.bar.baz

[export] namespace <name>[.<name>]*

• At least one name MUST be specified.
• CANNOT contain more than one . character in a row.
• CANNOT begin with . character.
• CANNOT end with . character.
• CANNOT start with a Reserved Name.

Examples

• foo
• foo.bar.baz
• language.v0
• collections.v0

Reserved Names

Any namespaces provided with a particular Ava distribution are considered reserved. This means that, for example, the following namespaces cannot be used:

• ava
• collections

Ava Namespace

The Ava namespace is automatically imported into every Ava file.

Exports

• Each file MAY export definitions using the export keyword.
• If the export keyword is used at the beginning of the namespace declaration, all definitions in the file are exported.
• Otherwise, definitions may be individually exported by prefixing them with the export keyword.

Export Syntax

export fn foo: () => Int32
    10
end fn

export enum Color
    object Red
    object Yellow
    object Blue
end enum

export namespace foo.bar.baz

export class Something
    fn foo: () => Int32
end class

Exporting Enumerations

For some enumeration, if the enum is exported, that means that all members of the enumeration are also exported.

Exporting Type Classes

If some type class is exported, all enclosed functions are also exported.

Imports

Imports immediately follow the namespace definition in each file. Each file may have zero or more imports. Imports bring definitions from another namespace into scope.

Import Syntax

Each import is a single, fully-qualified name. Imported names MAY be mapped to some alternative name using the as keyword. An import may refer to a specific namespace or it may refer to some specific definition within a namespace.

import <namespace>[.<definition name>|.*] [as <name>]

Importing Enumerations

Importing an enumeration does NOT import each member of the enumeration. Using some example enumeration:

export enum Color
    object Red
    object Yellow
    object Blue
end enum

The import and usage might be:

import foo.bar.baz.Color

let x: Color := Color.Red

Direct imports or * imports can bring members into direct scope:

import foo.bar.baz.Color
import foo.bar.baz.Color.*

let x: Color := Red

Importing Type Classes

When a type class is imported, its functions (both defined and instance-delegated) are made available and in scope for all types that satisfy that type class. All instances for the imported type class are resolved and made available. Type class instances cannot be imported directly.

• Only one instance may exist per class per type.
• instance are globally resolved.

Splat Imports

Splat imports, aka *, pull everything from the given path into scope. This means that all exported members are imported. Notably, this does NOT lift enumeration members into scope.

Examples

import collections.NonEmptyList as NEL
import collections.Queue
import collections.*
import collections as colls