On Wednesday, 21 June 2017 at 01:06:40 UTC, MysticZach wrote:
On Tuesday, 20 June 2017 at 21:04:16 UTC, Steven Schveighoffer
IMO, this whole proposal doesn't carry enough weight, either
your version or the DIP itself. I would not be in favor.
Current syntax is understandable, and not too verbose IMO.
That's a fair opinion. I wish I had a crystal ball to see how
many more people would use contracts if this DIP were accepted.
Well, one more datapoint for your prediction model, then: Not me.
I like DbC, but both what D currently has (too verbose) as well
as what this DIP does (see below) is not acceptable to me:
Enhancement 1 introduces significant cognitive dissonance for me
and I would argue that it also introduced a language
inconsistency by polluting the space between normal function
signature and body with ";". My brain keeps screaming "NO" when I
see it. Maybe I could get used to it, but if I allow "less than
ideal (within the limits of the language, of course)" as an
acceptable goal, I can just stick to checks like assert in the
function body; at least I (and most people reading my code) are
already familiar with that.
Enhancement 2 is fine in and of itself, but compounds the issues
caused by 1
Enhancement 3 introduces even more cognitive dissonance for me by
breaking the model that contracts are part of a functions
signature, not its body. I can also already do checks in the
function body as shown in the following, this enhancement is (at
best) superfluous to me:
---
int myFunc(Args...)(Args args)
if (Args.length > 2)
{
assert (args[0] != 0);
assert (args[1] > 1);
int result;
scope (success) assert (result > 0);
}
---
vs DIP Enhancement 3
---
int myFunc(Args...)(Args args)
if (Args.length > 2)
{
in assert (args[0] != 0);
in assert (args[1] > 1);
out (result) assert (result > 0);
}
---
What *I* need from a DIP that addresses DbC in D (to make it
viable for me) is to make the simple case as easy as possible to
read while not introducing language inconsistencies.
With that in mind I am strongly in favor of the syntax H. S. Teoh
already proposed:
---
int myFunc(Args...)(Args args)
if (Args.length > 2)
in (args[0] != 0)
in (args[1] > 1)
out (result => result > 0);
int myFunc(Args...)(Args args)
if (Args.length > 2)
in (args[0] != 0)
in (args[1] > 1)
out (result => result > 0) { ... }
---
- in contracts take a parenthesis delimited bool expression
- out contracts take a parenthesis delimited bool function
literal.
