[r6rs-discuss] Expansion order [was: Now, where were we?]
Andre van Tonder
andre at het.brown.edu
Tue Feb 24 15:51:45 EST 2009
On Tue, 24 Feb 2009, Christian Sloma wrote:
> On Tuesday 24 February 2009 21:01:58 Andre van Tonder wrote:
>> On Tue, 24 Feb 2009, Christian Sloma wrote:
>>>> Where is the burden on macro-free programs? (This is not meant to be
>>>> argumentative---I am genuinely trying to understand this criticism).
>>> Just one example: R6RS disallows the mixing of expression and definitions
>>> in libraries.
>> This restriction has nothing to do with macros, though. Expressions could
>> have been allowed easily, as you will see if you consider that even in R6RS
>> you can get the effect of an interleaved expression by simply making it the
>> RHS of a dummy definition.
> Note that it *has* to be inside a define, as the define marks the body to be
> delayed until all off the other definitions are evaluated.
The expansion process for <library body> could have been declared to be exactly
the same as the expansion process for <top-level body>, which allows interleaved
expressions that are not inside a define. The fact that it wasn't so defined
was just an arbitrary design choice.
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