[plt-scheme] define-unit meaning in combinator-example.ss?

You need to read chapter 7 "units' in the "*Reference*: PLT Scheme" doc.

Chongkai

Larry Evans wrote:
> While trying to understand:
>
>   (define-unit lambda-calc
>     ...)
>
> in:
>
>   plt/collects/combinator-parser/examples/combinator-example.ss
>
> I first searched the index:
>
>   /doc/guide/doc-index.html
>
> for 'define-unit'.  Since it wasn't there, I thought maybe it was
> defined in the current language.  Looking at the top of
> */combinator-example.ss, I saw:
>
>   (require scheme/unit
>          parser-tools/lex
>          combinator-parser/combinator-unit)
>
> So, I grep'ed the files scheme/unit and found:
>
> find . -name \*.ss -exec grep -e 'define-unit' {} \; -ls
>          (define-unit name imports exports elem ...))]))
> 16960391    4 -rw-r--r--   1 evansl   evansl       3302 Jun 13 20:50 
> ./unit/lang.ss
>
> which, with more context, is:
>
> (define-syntax (finish-a-unit stx)
>   (syntax-case stx (import export)
>     [(_ orig-stx name imports exports elem ...)
>      #'(begin
>          (provide name)
>          (define-unit name imports exports elem ...))]))
>
> So, I looked in the index to find that define-syntax defined:
>
> doc/guide/pattern-macros.html#(part._define-syntax_and_syntax-rules)
>
> however, there it's defined as:
>
>     (define-syntax id
>
>       (syntax-id-rules (literal-id ...)
>
>         [pattern template]
>
>         ...))
>
> which doesn't seem to match the:
>
>
> (define-syntax (finish-a-unit stx)
>
> in ./unit/lang.ss since (finish-a-unit stx) does not match, AFAICT,
> the id in '(define-syntax id'.
>
> So, how can I figure out what the 'define-unit' in
> combinator-example.ss means?
>
> Any help is appreciated.
>
>
> -regards,
> Larry
>