On Wednesday, 21 June 2017 at 18:04:07 UTC, Moritz Maxeiner wrote:
On Wednesday, 21 June 2017 at 17:55:05 UTC, MysticZach wrote:
Question: If `assert` itself allowed a user-defined hook, what
would the remaining justification be for decoupling `in` and
`out` contracts from the `assert` logic?
Because then you won't have normal asserts and contracts be
subject to different semantics?
If I use a library, I may very well want to disable the
library's internal assert checks (because I have enough
experience that it's working properly), but keep it's contracts
alive, because my code is still shiny new and riddled with bugs.
Timon appears to think that the checking logic is more
monolithic. From his reply above [1]:
"If [an alternative checking system is utilized], there should be
a way to hook into the checking logic. This has nothing at all to
do with contract syntax. asserts and contracts are coupled
already, as in-contracts form a disjunction on override by
catching AssertErrors."
So I'm hoping more people will weigh in on this issue. For
example, how easy is it to separate a library's internal
contracts from its external ones? Would you have to write
internal contracts in a different way from the ones facing the
user? How often is this distinction the one causing problems with
productivity?
The way I'm thinking about it would be that if there were a
pragma to turn off contracts in a particularly hot code path,
then the rest of the program could remain safe, while the fast
part was allowed to go as fast as possible, addressing the
performance issue.
But regarding the information issue, what kind of error
information is better delivered specifically through compiler
knowledge of `in` and `out` contracts, versus what it would
deliver in the same way via regular `assert`s? Or are all
contracts basically just fancy sugar for asserts at the beginning
and end of a function body? What can the compiler do with the
extra information? What can it say to the user that the user
wouldn't already be able to figure out if it were a regular
assert?
[1] http://forum.dlang.org/post/oie2nt$emf$1...@digitalmars.com
