On Fri, 22 Apr 2011 14:20:21 -0400, Robert Jacques <[email protected]>
wrote:
On Fri, 22 Apr 2011 13:22:31 -0400, Steve Schveighoffer
<[email protected]> wrote:
From: Robert Jacques <[email protected]>
[snip]
Forth, came the realization that in D2 'seconds' would probably be
pure, which would cause s.seconds = 5 to be compiler error.
No, it wouldn't be an error. s.seconds(5) is exactly the same as
TimeSpan.seconds(5), both would be callable as pure functions. In
other words, s isn't actually passed to the function, it's just used as
a namespace.
I apologize, pure alone wouldn't be enough to cause a compiler error. I
was thinking of the fact that DMD could/does error on expressions which
do nothing. However, pure wouldn't be enough to let the compiler know
'seconds = 5' does nothing. It would probably take a combination of
const/immutable + pure + nothrow, for DMD to detect that s.seconds = 5
could not possible produce useful work, and therefore should error.
P.S. On third thought, you'd really only need a const/immutable method, as
assignment of const/immutable variables is invalid. (This would require a
heuristic in DMD, etc). Also, given we can have static variables, static
methods should also be able to be const/immutable. But since static
variables are considered global state, perhaps pure covers those use
cases. Hmm... so maybe I was correct in that a strongly-pure function
called with field syntax should always be an error.
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