[r6rs-discuss] [Formal] Formal semantics should not contain complicating optimizations

[AndrevanTonder]

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This message is a formal comment which was submitted to formal-comment at r6rs.org, following the requirements described at: http://www.r6rs.org/process.html
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Name        : Andre van Tonder
Email       : andre at het.brown.edu
Type        : simplification
Priority    : low
Component   : Formal semantics
Version     : 5.92
Pages       : 61-73
Dependencies: None

Summary:
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The current formal semantics contains at least one, and possibly 
more, unnecessary performance optimizations that complicate it rather more than 
necessary.  Such optimizations have no place in a formal description of the 
semantics and should be removed.

Description:
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An example of such an optimization occurs on pages 69 and 70, where procedure
parameters are treated differently depending on whether they are the target
of set! in the body of the procedure.  This is unnecessary.  It clashes with 
the informal description in the body of the report, and it complicates
the semantics with an unnecessary rule [6appN], and an unnecessary variable 
assigment metafunction that takes about 25 lines (more than half of page 70) to 
describe.  Both of these, and possibly other rules depending on this 
distinction, should be removed.

This is one unnecessary complication, presumably based on optimization 
considerations, that I noticed.  A more careful reading may turn up other
optimization-related complications.  This formal comment is intended to apply
to all cases where the formal semantics may be simplified by discarding 
optimizations.