On Wednesday, 3 April 2013 at 05:42:13 UTC, Lars T. Kyllingstad
wrote:
The problem with assert is that it gets disabled in release
mode.
I think it is a bad idea to have this be the "standard"
behaviour of parameter validation.
Allow me to clarify my position on assert() a bit. As a general
rule, I think assert() should be used to verify internal program
flow and program invariants, and nothing more. Specifically,
public APIs should *not* change depending on whether asserts are
compiled in or not.
Say I am writing a function that you are using. I don't trust
you to always give me correct parameters, so I check them.
(Maybe my function could even do something dangerous if I didn't.)
public void myFunction(someArgs)
{
if (someArgs are invalid)
throw new InvalidArgumentError;
...
}
Now that I have verified that your input is correct, i.e. that
your part of the deal is done, everything that happens afterwards
is entirely up to me to get right. And *that* is when
assertations enter the picture. I'll sprinkle my code with
assert statements to make sure that every step of whatever
procedure myFunction() performs is correct, and I may use it to
verify input parameters to *private* helper functions and such.
These kinds of checks are purely for my personal use, for
debugging and for verifying that changes I make do not break
other parts of the code.
There may of course be situations, e.g. in performance-critical
code, where it is desirable to disable parameter validation, but
then -release should not be the switch that does it.
-version=TotallyUnsafeButVeryPerformantDudeYourAeOnYourOwnNow,
anyone? :)
Lars
