Re: Allowing "fall through" of attributes
On 07/19/2016 08:55 AM, Rufus Smith wrote:
I have some functions that take other functions. I would like the
attributes to be able to "fall" through so I get overload like behavior.
I only care that I am passing a function, not if it is shared,
extern(C), pure, @nogc, etc.
void foo(R, A...)(R function(A) bar)
{
alias type = typeof(bar);
pragma(msg, type);
// does magic with bar
}
foo never uses the attributes of bar explicitly. It uses type to
instantiate other functions like bar. I have to create a foo for each
attribute combination, which is not worth while. The code seems to break
only for extern, the best I can tell, most attributes do pass through.
But type does not contain these attributes.
functionAttributes may be useful. SetFunctionAttributes has an example:
https://dlang.org/phobos/std_traits.html#SetFunctionAttributes
Ali
Re: Allowing "fall through" of attributes
On Tuesday, 19 July 2016 at 17:10:35 UTC, Lodovico Giaretta wrote:
On Tuesday, 19 July 2016 at 17:05:55 UTC, Rufus Smith wrote:
On Tuesday, 19 July 2016 at 16:59:48 UTC, Lodovico Giaretta
wrote:
On Tuesday, 19 July 2016 at 16:50:56 UTC, Rufus Smith wrote:
On Tuesday, 19 July 2016 at 16:09:38 UTC, Lodovico Giaretta
wrote:
[...]
But this doesn't create a function with all the attributes
of the original? Just one that has the same return type and
parameters. What if Fun is pure or extern(C) or some other
attributes? I'd like to create a function that is exactly
the same in all regards as the original.
Sorry, I misunderstood your question.
With the method I showed you, if the function is @safe, pure,
@nogc or nothrow, foo will infer those attributes. But only
if the operations you do in foo (apart from calling bar) are
themselves @safe, pure, @nogc or nothrow.
For other things, like extern(C), I don't think there's a
simple solution; but I'm not an expert, so I hope someone
else will give you a better answer.
What is strange is I cannot even pass an extern(C) function to
foo.
void foo(R, A...)(R function(A) bar);
extern(C) void bar();
foo()
fails. Remove extern and it passes. I have not figured out how
to allow for extern(C) functions to be passed.
That's because an extern function must be called with a
different code. So it cannot be cast to a non-extern(C)
function pointer, which is what your foo accepts. If you follow
my advice, and make the entire function type a parameter of
foo, then foo will at least accept your extern(C) function, but
it will not be extern(C) itself.
I don't want it to be cast to a non-extern function. What I want
to do is create the exact same type of function that is passed to
the template except modify the arguments.
If I use a general parameter for the function, it accepts
extern(C), but I can't construct a function with it.
mixin("alias F = extern("~functionLinkage!Q~")
"~(ReturnType!Q).stringof~"
function"~(Parameters!Q).stringof~";");
gives me a type that looks to be what I want but I can't really
use it unless I want to declare the function that does the work
inside foo as mixin string.
One can't do extern(functionLinkage!Q) void baz() to create baz
with the proper linkage ;/
It looks like I might have to go the mixin way ;/ Going to be
messy ;/
Re: Allowing "fall through" of attributes
On Tuesday, 19 July 2016 at 17:05:55 UTC, Rufus Smith wrote: On Tuesday, 19 July 2016 at 16:59:48 UTC, Lodovico Giaretta wrote: On Tuesday, 19 July 2016 at 16:50:56 UTC, Rufus Smith wrote: On Tuesday, 19 July 2016 at 16:09:38 UTC, Lodovico Giaretta wrote: [...] But this doesn't create a function with all the attributes of the original? Just one that has the same return type and parameters. What if Fun is pure or extern(C) or some other attributes? I'd like to create a function that is exactly the same in all regards as the original. Sorry, I misunderstood your question. With the method I showed you, if the function is @safe, pure, @nogc or nothrow, foo will infer those attributes. But only if the operations you do in foo (apart from calling bar) are themselves @safe, pure, @nogc or nothrow. For other things, like extern(C), I don't think there's a simple solution; but I'm not an expert, so I hope someone else will give you a better answer. What is strange is I cannot even pass an extern(C) function to foo. void foo(R, A...)(R function(A) bar); extern(C) void bar(); foo() fails. Remove extern and it passes. I have not figured out how to allow for extern(C) functions to be passed. That's because an extern function must be called with a different code. So it cannot be cast to a non-extern(C) function pointer, which is what your foo accepts. If you follow my advice, and make the entire function type a parameter of foo, then foo will at least accept your extern(C) function, but it will not be extern(C) itself.
Re: Allowing "fall through" of attributes
On Tuesday, 19 July 2016 at 16:59:48 UTC, Lodovico Giaretta wrote: On Tuesday, 19 July 2016 at 16:50:56 UTC, Rufus Smith wrote: On Tuesday, 19 July 2016 at 16:09:38 UTC, Lodovico Giaretta wrote: [...] But this doesn't create a function with all the attributes of the original? Just one that has the same return type and parameters. What if Fun is pure or extern(C) or some other attributes? I'd like to create a function that is exactly the same in all regards as the original. Sorry, I misunderstood your question. With the method I showed you, if the function is @safe, pure, @nogc or nothrow, foo will infer those attributes. But only if the operations you do in foo (apart from calling bar) are themselves @safe, pure, @nogc or nothrow. For other things, like extern(C), I don't think there's a simple solution; but I'm not an expert, so I hope someone else will give you a better answer. What is strange is I cannot even pass an extern(C) function to foo. void foo(R, A...)(R function(A) bar); extern(C) void bar(); foo() fails. Remove extern and it passes. I have not figured out how to allow for extern(C) functions to be passed.
Re: Allowing "fall through" of attributes
On Tuesday, 19 July 2016 at 16:50:56 UTC, Rufus Smith wrote:
On Tuesday, 19 July 2016 at 16:09:38 UTC, Lodovico Giaretta
wrote:
On Tuesday, 19 July 2016 at 15:55:02 UTC, Rufus Smith wrote:
I have some functions that take other functions. I would like
the attributes to be able to "fall" through so I get overload
like behavior. I only care that I am passing a function, not
if it is shared, extern(C), pure, @nogc, etc.
void foo(R, A...)(R function(A) bar)
{
alias type = typeof(bar);
pragma(msg, type);
// does magic with bar
}
foo never uses the attributes of bar explicitly. It uses type
to instantiate other functions like bar. I have to create a
foo for each attribute combination, which is not worth while.
The code seems to break only for extern, the best I can tell,
most attributes do pass through. But type does not contain
these attributes.
You shall do something like this (please note that I didn't
check the docs while writing this; you shall definitely have a
look at std.traits and consider the following as pseudo-code
and not actual D):
void foo(Fun)(Fun bar)
if (isSomeFunction!Fun) // your constraint that bar is a
function
{
// how to get your R and A types, if you need them:
alias R = ReturnType!bar;
alias A = Parameters!bar;
alias type = Fun;
pragma(msg, type);
// do some magic
}
But this doesn't create a function with all the attributes of
the original? Just one that has the same return type and
parameters. What if Fun is pure or extern(C) or some other
attributes? I'd like to create a function that is exactly the
same in all regards as the original.
Sorry, I misunderstood your question.
With the method I showed you, if the function is @safe, pure,
@nogc or nothrow, foo will infer those attributes. But only if
the operations you do in foo (apart from calling bar) are
themselves @safe, pure, @nogc or nothrow.
For other things, like extern(C), I don't think there's a simple
solution; but I'm not an expert, so I hope someone else will give
you a better answer.
Re: Allowing "fall through" of attributes
On Tuesday, 19 July 2016 at 16:09:38 UTC, Lodovico Giaretta wrote:
On Tuesday, 19 July 2016 at 15:55:02 UTC, Rufus Smith wrote:
I have some functions that take other functions. I would like
the attributes to be able to "fall" through so I get overload
like behavior. I only care that I am passing a function, not
if it is shared, extern(C), pure, @nogc, etc.
void foo(R, A...)(R function(A) bar)
{
alias type = typeof(bar);
pragma(msg, type);
// does magic with bar
}
foo never uses the attributes of bar explicitly. It uses type
to instantiate other functions like bar. I have to create a
foo for each attribute combination, which is not worth while.
The code seems to break only for extern, the best I can tell,
most attributes do pass through. But type does not contain
these attributes.
You shall do something like this (please note that I didn't
check the docs while writing this; you shall definitely have a
look at std.traits and consider the following as pseudo-code
and not actual D):
void foo(Fun)(Fun bar)
if (isSomeFunction!Fun) // your constraint that bar is a
function
{
// how to get your R and A types, if you need them:
alias R = ReturnType!bar;
alias A = Parameters!bar;
alias type = Fun;
pragma(msg, type);
// do some magic
}
But this doesn't create a function with all the attributes of the
original? Just one that has the same return type and parameters.
What if Fun is pure or extern(C) or some other attributes? I'd
like to create a function that is exactly the same in all regards
as the original.
Re: Allowing "fall through" of attributes
On Tuesday, 19 July 2016 at 15:55:02 UTC, Rufus Smith wrote:
I have some functions that take other functions. I would like
the attributes to be able to "fall" through so I get overload
like behavior. I only care that I am passing a function, not if
it is shared, extern(C), pure, @nogc, etc.
void foo(R, A...)(R function(A) bar)
{
alias type = typeof(bar);
pragma(msg, type);
// does magic with bar
}
foo never uses the attributes of bar explicitly. It uses type
to instantiate other functions like bar. I have to create a foo
for each attribute combination, which is not worth while. The
code seems to break only for extern, the best I can tell, most
attributes do pass through. But type does not contain these
attributes.
You shall do something like this (please note that I didn't check
the docs while writing this; you shall definitely have a look at
std.traits and consider the following as pseudo-code and not
actual D):
void foo(Fun)(Fun bar)
if (isSomeFunction!Fun) // your constraint that bar is a
function
{
// how to get your R and A types, if you need them:
alias R = ReturnType!bar;
alias A = Parameters!bar;
alias type = Fun;
pragma(msg, type);
// do some magic
}
Allowing "fall through" of attributes
I have some functions that take other functions. I would like the
attributes to be able to "fall" through so I get overload like
behavior. I only care that I am passing a function, not if it is
shared, extern(C), pure, @nogc, etc.
void foo(R, A...)(R function(A) bar)
{
alias type = typeof(bar);
pragma(msg, type);
// does magic with bar
}
foo never uses the attributes of bar explicitly. It uses type to
instantiate other functions like bar. I have to create a foo for
each attribute combination, which is not worth while. The code
seems to break only for extern, the best I can tell, most
attributes do pass through. But type does not contain these
attributes.
