This library is used by Redex, which wants a `syntax'-like template
language, but for datum values instead of syntax objects. Using
`datum-case' and `datum' generates much less code. Redex uses
only a small part of the general functionality, so adding
`syntax/datum' could be overkill. It's implemented by generalizing
the `syntax-case' and `syntax' pattern matching and template
constructing code, though; it's not a lot of extra code, and it's
easiest to generalize completely. We may find other uses for
datum templates, too.
With the JIT, the `reverse' function is significantly faster,
while the `member' variants do not really change; the main
benefit is that the operations play well with futures.
The C implementation is still used when the JIT is unavailable,
since the Racket implementations can be much slower in
interpreted mode.
by default; a new optional argument restores the old behavior
(but the default behavior is consistent with the old docs and with
the vast majority of existing uses)
The implementation is ugly for performance reasons. A new primitive
`prop:arity-incomplete' property determines when to return #f for
`procedure-arity-includes?' in default mode. A nicer implementation
would be to redefine `procedure-arity-includes?' at the kw-proc level,
but the bytecode optimizer's and JIT's treatment of the built-in
`procedure-arity-includes?' is important. The implementation choice
could be revisited after cross-module inlining is implemented.
Closes PR 11978
