)feature-requirement ::= feature-identifier |
)feature-identifier ::= a symbol which is the name or alias of a SRFI
cond-expand form tests for the existence of features at
macro-expansion time. It either expands into the body of one of its
clauses or signals an error during syntactic
cond-expand expands into the body of the first clause
whose feature requirement is currently satisfied; the
clause, if present, is selected if none of the previous clauses is
The implementation has a set of
feature identifiers which are “present”, as well as a set
of libraries which can be imported.
The value of a
feature-requirement is determined by replacing each
#t if it is present
#t if library-name is importable (and
and then evaluating the resulting expression as a Scheme boolean expression
under the normal interpretation of
(cond-expand ((and srfi-1 srfi-10) (write 1)) ((or srfi-1 srfi-10) (write 2)) (else))
(cond-expand (command-line (define (program-name) (car (argv)))))
The second example assumes that
command-line is an alias for some
feature which gives access to command line arguments. Note that an error
will be signaled at macro-expansion time if this feature is not present.
You can use
java-9 to check if the underlying Java
is a specific version or newer.
For example the name
java-7 matches for
either Java 7, Java 8, or newer, as
You can use
class-exists:ClassName to check
ClassName exists at compile-time.
is roughly equivalent to the test
(library (org example MyClass)).
(The latter has some special handling for
(srfi ...) as well
as builtin Kawa classes.)
Returns a list of feature identifiers which
treats as true.
This not a complete list - for example
feature identifiers are not included.
It is an error to modify this list.
Here is an example of what
features might return:
(features) ⇒ (complex exact-complex full-unicode java-7 java-6 kawa ratios srfi-0 srfi-4 srfi-6 srfi-8 srfi-9 srfi-11 srfi-16 srfi-17 srfi-23 srfi-25 srfi-26 srfi-28 srfi-30 srfi-39 string-normalize-unicode threads)
These take one or more path names expressed as string literals,
find corresponding files, read the contents of the files in the specified order
as if by repeated applications of
read, and effectively
include with a
containing what was read from the files.
You can control the search path used for
by setting the
kawa.include.path property. For example:
$ kawa -Dkawa.include.path="|:/opt/kawa-includes"
"|" path element means to search
relative to the directory containing the including source file.
The default search path is
"|:." which means to first
search the directory containing the including source file,
and then search the directory specified by
The search path for
before the search path used by
include, so it always
searches first the directory containing the including source file.
Note that if the default search path is used then
include-relative are equivalent; there is only a difference
kawa.include.path property changes the default.
include-ci is like
include, except that it reads each
file as if it began with the