[Issue 3572] declaring pure function with void return type should be compile time error
https://issues.dlang.org/show_bug.cgi?id=3572
--- Comment #10 from Michal Minich ---
Agreed. even
pure void nothrow never() { assert(false); }
can throw Error, which is observable effect.
--
[Issue 3572] declaring pure function with void return type should be compile time error
https://issues.dlang.org/show_bug.cgi?id=3572
Dennis changed:
What|Removed |Added
Status|REOPENED|RESOLVED
CC||dkor...@live.nl
Resolution|--- |INVALID
--- Comment #9 from Dennis ---
(In reply to yebblies from comment #8)
> eg.
> pure void foo(string x)
> By definition calling foo does no observable work.
False.
```
pure void foo(string x) {
throw new Exception(x);
}
```
Here's a nothrow one:
```
pure nothrow void assertPositive(int x) {
assert(x > 0);
}
```
> While this might be WONTFIX or LATER like issue 3882, it is not invalid.
Until a case can be identified where there is actually "no observable work"
guaranteed, this is invalid.
(And even then, it's debatable whether "no observable work" is enough grounds
to make something not compile. `int x = 0; x += 0;` does nothing, but it does
and should compile.)
--
[Issue 3572] declaring pure function with void return type should be compile time error
http://d.puremagic.com/issues/show_bug.cgi?id=3572 yebblies yebbl...@gmail.com changed: What|Removed |Added Status|RESOLVED|REOPENED CC||yebbl...@gmail.com Version|2.036 |D2 Resolution|INVALID | Severity|normal |enhancement --- Comment #8 from yebblies yebbl...@gmail.com 2013-03-06 21:46:46 EST --- (In reply to comment #7) In current, we can declare a pure function which has weak purity. pure void foo(int* p, out string s, ref int[] arr); All results are returned through its parameters. So, returning void itself has no problem in pure functions. This would still be meaningful for strongly-pure or const-pure functions. eg. pure void foo(string x) By definition calling foo does no observable work. While this might be WONTFIX or LATER like issue 3882, it is not invalid. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3572] declaring pure function with void return type should be compile time error
http://d.puremagic.com/issues/show_bug.cgi?id=3572 Andrej Mitrovic andrej.mitrov...@gmail.com changed: What|Removed |Added CC||andrej.mitrov...@gmail.com --- Comment #6 from Andrej Mitrovic andrej.mitrov...@gmail.com 2013-02-03 15:53:14 PST --- (In reply to comment #3) (In reply to comment #2) ? Why would you allow out parameters in a pure function? This seems reasonable for simple value types (ints, floats, etc.), but when you start passing objects in, you start allowing the modification of whole object subgraphs from pure functions. This makes no sense. Why doesn't it make sense? Aren't you thinking of inout parameters? A pure function void foo(out A a); ought to be exactly the same as A foo(); together with an assignment. I'm not seeing anything impure in that. BTW, it works fine in CTFE. (CTFE isn't quite the same concept as pure, but it's close). Should we close this report then? -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3572] declaring pure function with void return type should be compile time error
http://d.puremagic.com/issues/show_bug.cgi?id=3572 Kenji Hara k.hara...@gmail.com changed: What|Removed |Added Status|NEW |RESOLVED Resolution||INVALID --- Comment #7 from Kenji Hara k.hara...@gmail.com 2013-02-03 18:50:45 PST --- In current, we can declare a pure function which has weak purity. pure void foo(int* p, out string s, ref int[] arr); All results are returned through its parameters. So, returning void itself has no problem in pure functions. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3572] declaring pure function with void return type should be compile time error
http://d.puremagic.com/issues/show_bug.cgi?id=3572 Trass3r mrmoc...@gmx.de changed: What|Removed |Added Keywords||accepts-invalid, diagnostic CC||mrmoc...@gmx.de Platform|x86 |All OS/Version|Windows |All Severity|enhancement |normal --- Comment #5 from Trass3r mrmoc...@gmx.de 2012-01-05 14:19:40 PST --- Also you shouldn't be able to throw away the result of a pure function. http://d.puremagic.com/issues/show_bug.cgi?id=7235 -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3572] declaring pure function with void return type should be compile time error
http://d.puremagic.com/issues/show_bug.cgi?id=3572 --- Comment #4 from David Simcha dsim...@yahoo.com 2010-02-17 18:38:36 PST --- (In reply to comment #3) Why doesn't it make sense? Aren't you thinking of inout parameters? A pure function void foo(out A a); ought to be exactly the same as A foo(); together with an assignment. I'm not seeing anything impure in that. BTW, it works fine in CTFE. (CTFE isn't quite the same concept as pure, but it's close). You're right, I did get confused between out and ref. Allowing out parameters in pure functions makes sense. I tend to forget how out parameters work because I almost never use them. I almost always just return a tuple or a struct. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3572] declaring pure function with void return type should be compile time error
http://d.puremagic.com/issues/show_bug.cgi?id=3572 Don clugd...@yahoo.com.au changed: What|Removed |Added CC||clugd...@yahoo.com.au --- Comment #1 from Don clugd...@yahoo.com.au 2009-12-04 12:01:56 PST --- (In reply to comment #0) In D specification is written: Pure functions are functions that produce the same result for the same arguments. To that end, a pure function has parameters that are all immutable or are implicitly convertible to immutable void function cannot produce any result, thus they are meaningless as pure functions. Also when all parameters are implicitly immutable, there is no possibility to modify out parameters. So the only way for function to produce result, is by returning it (and void has no value). I think the restriction on 'out' parameters will be removed. I don't think there's any reason for it. A void pure function that doesn't have any 'out' parameters does seem to be pretty useless (you can use it as a metaprogramming test that anything inside it is pure, but that's about all I can think of). -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3572] declaring pure function with void return type should be compile time error
http://d.puremagic.com/issues/show_bug.cgi?id=3572 --- Comment #3 from Don clugd...@yahoo.com.au 2009-12-04 18:28:11 PST --- (In reply to comment #2) ? Why would you allow out parameters in a pure function? This seems reasonable for simple value types (ints, floats, etc.), but when you start passing objects in, you start allowing the modification of whole object subgraphs from pure functions. This makes no sense. Why doesn't it make sense? Aren't you thinking of inout parameters? A pure function void foo(out A a); ought to be exactly the same as A foo(); together with an assignment. I'm not seeing anything impure in that. BTW, it works fine in CTFE. (CTFE isn't quite the same concept as pure, but it's close). -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
