Standard library

ABS comes bundled not only with an array of builtin types and functions, but also with a few modules to ease your development process: we refer to this modules as the "standard library", "standard modules" or stdlib.

Requiring a standard library module

Standard library modules are required the same way you'd require any other external module, by using the require(...) function; the only difference is that standard modules use the @ character as prefix, for example:

mod = require('@module')  # Loads "module" from the standard library
mod = require('./module') # Loads "module" from the current directory
mod = require('module')   # Loads "module" that was installed through the ABS package manager

Technical details

The ABS standard library is developed in ABS itself and available for everyone to see (and poke with) at github.com/abs-lang/abs/tree/master/stdlib (opens new window).

The @cli library, for example, is a simple ABS script of less than 100 lines of code:

# CLI app
cli = {}

# Commands registered within this CLI app
cli.commands = {}

# Function used to register a command
cli.cmd = f(name, description, flags) {
    return f(fn) {
        cli.commands[name] = {};
        cli.commands[name].cmd = f() {
            # Create flags with default values
            for k, _ in flags {
                v = flag(k)

                if v {
                    flags[k] = v
                }
            }

            # Call the original cmd
            result = fn.call([args()[3:], flags])

            # If there's a result we print it out
            if result {
                echo(result)
            }
        }

        cli.commands[name].description = description
    }
}

# Run the CLI app
cli.run = f() {
    # ABS sees "abs script.abs xyz"
    # so the command is the 3rd argument
    cmd = arg(2)

    # Not passing a command? Let's print the help
    if !cmd {
        return cli.commands['help'].cmd()
    }

    if !cli.commands[cmd] {
        exit(99, "command '${cmd}' not found")
    }

    return cli.commands[cmd].cmd()
}

# Add a default help command that can be
# overridden by the caller
@cli.cmd("help", "print this help message", {})
f help() {
    echo("Available commands:\n")

    for cmd in cli.commands.keys().sort() {
        s = "  * ${cmd}"

        if cli.commands[cmd].description {
            s += " - " + cli.commands[cmd].description
        }

        echo(s)
    }
}

return cli