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
Still holding out hope Walter will change his mind here..
His rationale is based on keeping code clean and organized, but
given that D has no preprocessor macros, it will never look as
bad as C++ code, or even close.
Compounding versions in C++ accounts for a very small portion of
the mess. When you have an #if VERS every 5 lines, however,
you've got a problem...but then, you can do that with D's version
just the same. The real solution is to properly encapsulate
system-dependant code so that whatever version statement you
need, is all in one place. Also when you have to hack 10
different macros together to invent a feature your language
doesn't have, you've got a problem, but this is much less of a
concern in D than C++.
When even D gurus writing D compilers have to hack solutions
together with static if to get by, its time to re-evaluate the
situation.
Bit
