/*6.8 Versioning*/
/Libraries and import clauses optionally carry versioning
information. This allows reflecting the development history of a
library, but also significantly increases the complexity of the
library system. Experience with module systems gathered in other
languages as well as with shared libraries at the operating-system
level consistently indicates that relying only on the name of a
module for identification causes conflicts impossible to rectify in
the absence of versioning information, and thus diminishes the
opportunities for sharing code. Therefore, versioning is part of the
library system.
/
/
/
This part of the rationale makes no sense:
/Experience with module systems gathered in other languages as well
as with shared libraries at the operating-system level consistently
indicates that relying only on the name of a module for
identification causes conflicts impossible to rectify in the absence
of versioning information,
/
/
/Module version numbers are very commonly used at the systems level,
that much is true enough. Module version numbers are used to name some
installed libraries. Module version numbers often appear in
"configure" scripts, "Makefiles," and other software configuration programs.
Experience with module systems in other languages often points to
successes in which, within program texts, version numbers are left out
and simple names are used for modules. The "hello world" program
imports <stdio.h>, not <IEEE stdio.h 1003 1 1998>. The author of the
rationale is a guilty of a gross exaggeration, at the least.
The assertion that there are "conflicts impossible to rectify in the
absence of [version numbers]" is a very strong claim, an implausible
claim, and a claim that is unsupported here.
The rationale also does not address at all the question of why a lexical
ordering of lists of numbers is a good choice even if we accept that
simple names alone are not enough. Why a list of numbers? Why not a
matrix? Why not a generalized tree of numbers? Why not allow
characters and strings in, along with numbers? More complicated
structures like that occur commonly in the real world, as for example
when someone names their revision of a library by copying some other
version number, adding a branch name, and then adding a branch version
number (e.g., "bsd-1.2-newvmsystemfork-0.1").
All such details of the present design for Scheme seem to refer to some
vague analogy to experience with "other languages" and "shared libraries
at the operating-system level" and given that that analogy is so poorly
presented, there is no rationale presented here at all!
-t
(p.s.: I care not if, as a pragmatic condition of getting lots of open
source Scheme modules in various package systems, a library naming
system that includes version numbers is widely adopted. I care only
that such is not made normative for Scheme itself.)
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