Fwd: Re: definition in expression context, where definitions are not allowed

Fwd: Re: definition in expression context, where definitions are not allowed

[Arne Babenhauserheide]

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Hi David,

Thank you for answering!

May I send my reply to guile-devel?

Am Sonntag, 11. Oktober 2015, 09:58:59 schrieb David Kastrup:
> > Or am I missing something else which is enabled by this limitation?
> 
> A function defined with `define' may call a function defined in a
> _following_ `define'.  How do you make that work when a statement
> in-between can already call the first function?

So this is a guarantee that all defines in a block of defines can call
each other?

I now looked it up in r7rs small.[1]

> Definitions can occur at the beginning of a body (that
> is, the body of a lambda, let, let*, letrec, letrec*,
> let-values, let*-values, let-syntax, letrec-syntax,
> parameterize, guard, or case-lambda).

> An expanded body containing internal definitions can al-
> ways be converted into a completely equivalent letrec*
> expression.

So essentially this is just explicit scoping, as with let. And let
proved to me that it works better than just assigning anywhere
(because it doesn’t have a large overhead).

So I think what threw me off is mainly the error message: 

> definition in expression context, where definitions are not allowed

This does not tell me how I can do what I intended to. “all
definitions must be at the beginning of the body. You can for example
create a new scope with let ().”

Best wishes,
Arne

[1]: http://trac.sacrideo.us/wg/wiki/R7RSHomePage
     http://trac.sacrideo.us/wg/raw-attachment/wiki/WikiStart/r7rs.pdf
     5.3.2, page 26

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