Import

Typically, Bril programs are self-contained: they only use functions defined elsewhere in the same program. This import extension lets Bril code use functions defined in other files.

A Bril import refers to a file and lists the functions to import from it, like this:

{
    "path": "my_library.json",
    "functions": [{"name": "libfunc"}]
}

This import assumes that there’s a Bril file called my_library.json, and that it declares a function @libfunc. The current Bril file may now invoke @libfunc as if it were defined locally.

Syntax

The top-level Bril program is extended with an imports field:

{ "functions": [<Function>, ...], "imports": [<Import>, ...] }

Each import object has this syntax:

{
    "path": "<string>",
    "functions": [
        { "name": "<string>", "alias": "<string>"? },
        ...
    ]
}

The path is a relative reference to a Bril JSON file containing the functions to import. In the objects in the functions list, the name is the original name of the function, and the optional alias is the local name that the program will use to refer to the function. A missing alias makes the local name equal to the original name.

It is an error to refer to functions that do not exist, or to create naming conflicts between imports and local functions (or between different imports). Import cycles are allowed.

Text Format

In Bril’s text format, the import syntax looks like this:

from "something.json" import @libfunc, @otherfunc as @myfunc;

Search Paths

We do not define the exact mechanism for using the path string to find the file to import. Reasonable options include:

• Resolve the path relative to the file the import appears in.
• Use a pre-defined set of library search paths.

We only specify what it means to import JSON files; implementations can choose to allow importing other kinds of files too (e.g., text-format source code).