On Tuesday, 10 May 2016 at 11:12:58 UTC, Tomer Filiba wrote:
Hey guys,
Looking at our code base (weka), I realized it would be really
useful if we had logical operators (negation, conjunction,
disjunction) in the version's "condition" clause. Here's what I
have in mind:
version(!extra_checks) {
...
}
version(dlang_ver_2069 || dlang_ver_2070) {
...
}
Today we have lots of ugly code like
version(unittest) {} else { ... }
and bad-old copy-paste for the logical-or case I mentioned.
Is there any reason for that versions can't take compound
logical conditions? Alternatively, an isVersion(x) predicate
that I could use in a static if could do the trick -- although
I think ``version(x || y)`` is more readable than ``static if
(isVersion(x) || isVersion(y))``
I think it could be a useful feature. Any thoughts?
-tomer
This has been discussed multiple times in the forum, Walter is
against it and I agree with him:
http://forum.dlang.org/thread/[email protected]
http://forum.dlang.org/thread/[email protected]
Static if can do this now using enums that you define by using
those version conditions, but Walter advises against it.
Another alternative is to put all such OS versioning logic in a
build script somewhere and then version on features in your D
code, which is probably cleanest, ie have a build script check if
you're building for an OS that supports LIBRARY_X, then pass
-version=LIBRARY_X to your build and version your D code using
version(LIBRARY_X). If you use reggae
(https://github.com/atilaneves/reggae), the logic that checks if
you're using LIBRARY_X could be written in D too.
The idea is to avoid having a bunch of such repeated conditional
logic for versioning spread throughout the codebase, because it
will be very error-prone and brittle.
