Re: Expression/Definition dependency semantics
Dr. Arne Babenhauserheide 25 Sep 2023 09:47 UTC
Daphne Preston-Kendal <xxxxxx@nonceword.org> writes:
> On 24 Sep 2023, at 18:13, Dr. Arne Babenhauserheide <xxxxxx@web.de> wrote:
>> "It is an error for the evaluation of any expression to require
>> knowledge of the value of a variable whose definition is to the right of
>> the expression."
> More generally, if we were to allow what you asked for, there would be
> no reason not to allow general use before definition
I’m not asking you about allowing that but about not adding language
that restricts what does not change in the SRFI.
R7RS 5.3.2 already states “it is an error if it is not possible to
evaluate each <expression> of every internal definition in a <body>
without assigning or referring to the value of the corresponding
<variable> or the <variable> of any of the definitions that follow it in
<body>”.
There is no need to duplicate that.
The change in the SRFI is that expressions can be written in between the
defines. How defines interact with each other does not change, so the
rule in the SRFI does not need to mention definitions referencing other
definitions at all.
If you want to make sure that this is not misread as relaxing the rule
on definitions, maybe add a reference to R7RS 5.3.2? “For definitions,
section 5.3.2 of R7RS small continues to apply”?
Best wishes,
Arne
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