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Command line argument parser for Io language
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OptionParser is a command line parser object for Io, which hopefully makes writing command line tools a little easier.

Quick example

This is a trivial usage example: Command

echo := command(msg,
    msg perform(
        if(nonewline, "print", "println")
) with(
    list("n", "nonewline", false, "don't print a newline")
) doc("A simple echo command.")

if(isLaunchScript, echo)

Running the above script without any argument will bring up the help text: % io

A simple echo command.


  -h --help       show help
  -n --nonewline  don't print a newline

Note: The number of positional arguments should match the number of arguments declared in the command body, since each declared argument gets binded to the corresponding command line positional argument.

command objects can also be executed just as method objects, in that case the locals object of the command will be populated from the default option values:

% io "Hello world\!"
Hello world!
| Running `echo` with no arguments.

Hello world!
| Running `echo` as a method.
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