This is a proposal for cond-expand in R7RS small Scheme. I am publishing
this document to invite wide comment. There is nothing official about
it. I acknowledge the kind help of members of the r6rs-discuss mailing
list and the #scheme IRC channel in the discussions that led up to
this document. However, I retain sole responsibility for it, including
all errors.
Cond-expand as explained in SRFI 0 doesn't explain where the feature
identifiers come from. I'm proposing the following list. A small Scheme
implementation has the feature identifier if it has the feature.
thing-one (temporary name)
All R7RS small Scheme implementations have this feature.
exact-closed
All rational operations on exact values produce exact values, with
the possible exception of /. If an implementation restriction
is reached, an error is signaled. If this feature identifier
is missing, some results may be inexact.
ratios
/ with exact arguments produces an exact result.
ieee-float
Inexact numbers are IEEE 754 floating point values. This implies
support for +inf.0, -inf.0, +nan.0, and -0.0.
full-unicode
All Unicode characters are supported
windows
This Scheme implementation is running on Windows.
posix
This Scheme implementation is running on a Posix system.
unix, darwin, linux, bsd, netbsd, openbsd, freebsd, ...
OS-specific flags.
i386, x86_64, ppc, sparc, sparc64, ...
CPU-specific flags.
ilp32, lp64, ilp64, ...
C-memory-model-specific flags.
<name>
The name of this implementation.
<name>-<version>
The name and version of this implementation.
<other>
Anything implementation-specific.
In addition, if a module is _importable_, then its name appears in the
feature identifiers list (now something of a misnomer, since not all
module names are identifiers). A module is importable if it is:
already loaded and imported;
already loaded but not currently imported;
not loaded, but known to exist due to an implementation-specific
mapping between (at least some) module names and external entries
such as file names.
--
John Cowan [email protected] http://www.ccil.org/~cowan
Dievas dave dantis; Dievas duos duonos --Lithuanian proverb
Deus dedit dentes; deus dabit panem --Latin version thereof
Deity donated dentition;
deity'll donate doughnuts --English version by Muke Tever
God gave gums; God'll give granary --Version by Mat McVeagh
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