# define-options

define-options is a convenience macro for getopt-long for Chicken
Scheme.

[getopt-long] is already super comfortable to use but let's sand
down those edges even more!

    (define-options program-names grammar)

The program-names is a symbol or list of symbols that the program's
binary or script is going to be called.

The grammar is your standard [getopt-long] grammar but with one
extension; options can now have a "default" property.

It terminates on unhandled options or when using the -h or --help
option and prints usage.

It also binds each option to a name.

So, for example, here is the define-options call from [7off][7off]:

    (define-options
      (7off)
      '((allow-wack-headers
        "Allow skipping header levels instead of enforcing tree layout."
        (single-char #\w))
       (disable-warnings
        "Suppress warnings and lintings."
        (single-char #\q))
       (help
        "Print this help text."
        (single-char #\h))
       (input-file
        "Input file name."
        (single-char #\i)
        (value #t))
       (output-file
        "Output file name."
        (single-char #\o)
        (value #t))
       (default-alt
         "Alt text for verbatim blocks."
         (single-char #\a)
         (value #t)
         (default "Code"))
       (polish
        "Polish quotes and dashes."
        (single-char #\p))))

This example will define the variables `allow-wack-headers`,
`disable-warnings`, `help`, `input-file`, `output-file`,
`default-alt`, and `polish`.

`define-options` can also take an optional third argument, a list
of arguments to supply when the program is not being called from the
command line. While this is useless in production code, it's awesome
when testing and developing your program at the REPL. It's an
implicitly quoted list of strings, so just paren wraps some strings
you'd wanna pass. For example `("-p" "-a" "Zebra"
"--allow-wack-headers")`.

[getopt-long]: http://wiki.call-cc.org/eggref/5/getopt-long
[7off]: https://idiomdrottning.org/7off