[racket] the definition of 'form'?

If you refer to the "Syntax Model" section of the reference 
(http://docs.racket-lang.org/reference/syntax-model.html), you'll see 
that Racket syntax is defined by two passes, called "read" and "expand".

The grammar you gave in your message is what I would call a 
"term"---it's anything that the read pass can turn into a syntax object. 
In other words, terms are what syntax objects represent.

The word "form" generally means any of the non-terminals of the Racket 
language that the macro expander cares about, such as "expression forms" 
and "definition forms". There are also "module-level forms", which 
include require and provide. There's a list of these nonterminals in the 
subsection "Fully Expanded Programs" 
(http://docs.racket-lang.org/reference/syntax-model.html#%28part._fully-expanded%29). 
You can think of the syntax of Racket roughly as that grammar with "or a 
macro that eventually expands into one of the above" added to every 
production there---except the one for "formals". The "formals" 
non-terminal doesn't correspond to an expansion context, nor do 
"module-path" or "raw-require-spec"; thus, they are not considered 
forms. Neither is something like "cond-clause", for example; it's just 
an auxiliary non-terminal for the "cond" macro.

To complicate matters, macros can also create new expansion contexts and 
thus new kinds of forms. For example, the class macro introduces 
"class-body forms", which include expressions and definitions as well as 
other syntaxes that are only significant immediately within class 
bodies, such as "init" and "abstract" forms.

Ryan


On 05/16/2014 12:28 PM, Norman Ramsey wrote:
> Where would I find out, preferably in the Racket documentation,
> the definition of what a 'form' is?  I'm thinking along these lines:
>
>    A form is one of:
>      - a symbol
>      - a numeric literal
>      - a string literal
>      - ... possibly other literals? ...
>      - a sequence of forms wrapped in one pair of parentheses
>
> Is this the right idea?  Or is the word 'form' reserved only for
> things wrapped in parentheses?
>
>
> Norman
>
>
> P.S. In the Racket documentation, I found the section on 'Syntactic
> Forms', but I haven't found a definition of what a form is, and I
> haven't found the word 'form' in the index.
>
>
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