Re: Calling dynamically bound functions from weakly pure function
On Tuesday, 22 July 2014 at 13:35:27 UTC, Rene Zwanenburg wrote:
On Saturday, 19 July 2014 at 11:12:00 UTC, Marc Schütz wrote:
Casting to pure would break purity if the called function is
not actually pure. AFAIU, the problem is that the mutable
function pointers are not accessible from inside the pure
function at all, in which case the solution is to cast them to
immutable, not to pure.
Indeed that is the problem. I didn't think of casting to
immutable, that should work..
But to cast something, you'd need to have access to it in the
first place...
This seems to work:
int function(int) pure my_func_ptr;
struct CallImmutable {
static opDispatch(string fn, Args...)(Args args) {
return mixin(fn)(args);
}
}
int test() pure {
return CallImmutable.my_func_ptr(1);
}
But I suspect it's because of a bug.
`CallImmutable.opDispatch` should not be deduced to be pure,
and this not be callable from `test`.
Yeah that looks like a bug. I should be able to conjure
something up, perhaps using assumeUnique, that won't break in
newer versions.
Thanks for the answers!
Filed as:
https://issues.dlang.org/show_bug.cgi?id=13187
Re: Calling dynamically bound functions from weakly pure function
On Saturday, 19 July 2014 at 11:12:00 UTC, Marc Schütz wrote:
Casting to pure would break purity if the called function is
not actually pure. AFAIU, the problem is that the mutable
function pointers are not accessible from inside the pure
function at all, in which case the solution is to cast them to
immutable, not to pure.
Indeed that is the problem. I didn't think of casting to
immutable, that should work..
But to cast something, you'd need to have access to it in the
first place...
This seems to work:
int function(int) pure my_func_ptr;
struct CallImmutable {
static opDispatch(string fn, Args...)(Args args) {
return mixin(fn)(args);
}
}
int test() pure {
return CallImmutable.my_func_ptr(1);
}
But I suspect it's because of a bug. `CallImmutable.opDispatch`
should not be deduced to be pure, and this not be callable from
`test`.
Yeah that looks like a bug. I should be able to conjure something
up, perhaps using assumeUnique, that won't break in newer
versions.
Thanks for the answers!
Re: Calling dynamically bound functions from weakly pure function
Broken purity deduction is less critical than broken purity check. We can hit the latter somewhere else.
Re: Calling dynamically bound functions from weakly pure function
On 07/19/2014 03:53 PM, Kagamin wrote: It's ok to deduce opDispatch as pure, but then its purity should be enforced and error reported. Why would it be ok to deduce opDispatch as pure only to report an error that it is not actually pure? This would be a bug as well (albeit none that causes unsoundness.)
Re: Calling dynamically bound functions from weakly pure function
It's ok to deduce opDispatch as pure, but then its purity should be enforced and error reported.
Re: Calling dynamically bound functions from weakly pure function
On Friday, 18 July 2014 at 16:19:20 UTC, John Colvin wrote:
On Friday, 18 July 2014 at 16:12:18 UTC, Rene Zwanenburg wrote:
On Friday, 18 July 2014 at 15:57:40 UTC, John Colvin wrote:
On Friday, 18 July 2014 at 14:15:46 UTC, Rene Zwanenburg
wrote:
For all intents and purposes, the following code can be
weakly pure:
struct VAO
{
}
urrmm. Did you mean to post more than that?
Haha yup. Not sure what happened there.
I'm a bit short on time at the moment, but what it comes down
to is that Derelict loads functions from DLL's and assigns
them to global function pointers. Of course, these function
pointers have to be mutable.
Is there a nice way to call such functions from a pure
function?
I haven't tried it, but can you cast the function references to
be pure?
Casting to pure would break purity if the called function is not
actually pure. AFAIU, the problem is that the mutable function
pointers are not accessible from inside the pure function at all,
in which case the solution is to cast them to immutable, not to
pure.
But to cast something, you'd need to have access to it in the
first place...
This seems to work:
int function(int) pure my_func_ptr;
struct CallImmutable {
static opDispatch(string fn, Args...)(Args args) {
return mixin(fn)(args);
}
}
int test() pure {
return CallImmutable.my_func_ptr(1);
}
But I suspect it's because of a bug. `CallImmutable.opDispatch`
should not be deduced to be pure, and this not be callable from
`test`.
Re: Calling dynamically bound functions from weakly pure function
On Friday, 18 July 2014 at 16:12:18 UTC, Rene Zwanenburg wrote:
On Friday, 18 July 2014 at 15:57:40 UTC, John Colvin wrote:
On Friday, 18 July 2014 at 14:15:46 UTC, Rene Zwanenburg wrote:
For all intents and purposes, the following code can be
weakly pure:
struct VAO
{
}
urrmm. Did you mean to post more than that?
Haha yup. Not sure what happened there.
I'm a bit short on time at the moment, but what it comes down
to is that Derelict loads functions from DLL's and assigns them
to global function pointers. Of course, these function pointers
have to be mutable.
Is there a nice way to call such functions from a pure function?
I haven't tried it, but can you cast the function references to
be pure?
Re: Calling dynamically bound functions from weakly pure function
On Friday, 18 July 2014 at 15:57:40 UTC, John Colvin wrote:
On Friday, 18 July 2014 at 14:15:46 UTC, Rene Zwanenburg wrote:
For all intents and purposes, the following code can be weakly
pure:
struct VAO
{
}
urrmm. Did you mean to post more than that?
Haha yup. Not sure what happened there.
I'm a bit short on time at the moment, but what it comes down to
is that Derelict loads functions from DLL's and assigns them to
global function pointers. Of course, these function pointers have
to be mutable.
Is there a nice way to call such functions from a pure function?
Re: Calling dynamically bound functions from weakly pure function
On Friday, 18 July 2014 at 14:15:46 UTC, Rene Zwanenburg wrote:
For all intents and purposes, the following code can be weakly
pure:
struct VAO
{
}
urrmm. Did you mean to post more than that?
Calling dynamically bound functions from weakly pure function
For all intents and purposes, the following code can be weakly
pure:
struct VAO
{
}
