[r6rs-discuss] [Formal] Conflating programs and scripts

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Name        : Andre van Tonder
Email       : andre at het.brown.edu
Type        : defect
Priority    : medium
Component   : Scripts
Version     : 5.91
Pages       : 26-27
Dependencies: None
Summary:
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The report conflates three orthogonal issues - defining a program,
marking the entry point of the program, and marking the program as one 
particular kind of Scheme program on one particular operating system in one 
particular use case.
Description:
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The report conflates three orthogonal issues - defining a program,
marking the entry point of the program, and marking the program as one 
particular kind of Scheme program on one particular operating system in one 
particular use case, a use case that, by many Schemers, is not commonly needed, 
if at all.
The current report is allowing this one use case to
strongly biase the way Scheme programs are supposed to be
organised in files.  Although it is not required by the report,
implementations are likely to satisfy it by requiring the "main"
part of the program (in the script) to be in a separate file
from the rest, even when it makes no logical organizational
sense to do this.
An existence proof:  Many current Schemes allows one to write
portable programs that will run on various operating systems,
including Unix, without having to include any operating-system
specific details in the text of the program.
A more common use case for many is compiling a program to an
executable binary.  These do not require a scheme-script executable
to run, nor do they require special directives to satisfy an
infrastructure requirement for use case they do not need on one
particular operating system.   The report therefore burdens,
and discriminates against, compiler-only implementations by
requiring them to provide unneeded facilities.
Presumably the intent of the authors is that a file containing a
script can be dropped without modification onto any system and will
just work.  But the report states that the first line may contain
something else, and should be ignored.  The report also does not
explicitly require the script part of a program to be in a separate
file, nor the #! directive to be on the first  line of such a file.
However, in these cases, presumably it will not portably run on Unix.
In other words, the report blesses non-portable programs.  What is then
the point of going to the trouble of specifying something in the interest
of portablity if it does not guarantee portability.
Marking the interpreter as part of the program text is an
idiosyncratic practice particular to unix scripts, conflating
orthogonal concerns.  The Unix design is not necessarily a particularly
good design.  It should not be adopted and blessed by the Scheme report.
A large number of current and future Schemers do not often, if ever, use Unix.
Suggestion:
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Consider providing a definition of Scheme programs either instead of, or in 
addition to, scripts, or modify the script specification by removing the
<script header> and most of the substance of 7.1.1., in a way that does
not accomodate, bless or otherwise favour a particular use case on a particular 
operating system.  Allow programs to consist of libraries and entry point in the 
same contiguous text.