Mixing
Is it possible to write a c++ std::function that returns itself as a type? [duplicate]
This question already has an answer here:
Recursive typedef function definition : std::function returning its own type
3 answers
Let's start with a simple typedef of a function:
typedef std::function<uint32_t(SomeStruct *)> HandlerFunction;
Here we have a function that returns a uint32_t and takes a pointer to SomeStruct.
What I would like to do is modify this function so it returns a type of itself, something like this:
typedef std::function<HandlerFunction(SomeStruct *)> HandlerFunction;
Obviously that won't compile, but it represents the end goal I'm trying to achieve.
c++
asked Nov 19 '18 at 15:12
Michael Gantz
6525
marked as duplicate by SergeyA c++
Users with the c++ badge can single-handedly close c++ questions as duplicates and reopen them as needed.
StackExchange.ready(function() {
if (StackExchange.options.isMobile) return;
$('.dupe-hammer-message-hover:not(.hover-bound)').each(function() {
var $hover = $(this).addClass('hover-bound'),
$msg = $hover.siblings('.dupe-hammer-message');
$hover.hover(
function() {
$hover.showInfoMessage('', {
messageElement: $msg.clone().show(),
transient: false,
position: { my: 'bottom left', at: 'top center', offsetTop: -7 },
dismissable: false,
relativeToBody: true
});
},
function() {
StackExchange.helpers.removeMessages();
}
);
});
});
Nov 19 '18 at 15:26
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
|
show 1 more comment
This question already has an answer here:
Recursive typedef function definition : std::function returning its own type
3 answers
Let's start with a simple typedef of a function:
typedef std::function<uint32_t(SomeStruct *)> HandlerFunction;
Here we have a function that returns a uint32_t and takes a pointer to SomeStruct.
What I would like to do is modify this function so it returns a type of itself, something like this:
typedef std::function<HandlerFunction(SomeStruct *)> HandlerFunction;
Obviously that won't compile, but it represents the end goal I'm trying to achieve.
c++
asked Nov 19 '18 at 15:12
Michael Gantz
6525
marked as duplicate by SergeyA c++
Users with the c++ badge can single-handedly close c++ questions as duplicates and reopen them as needed.
StackExchange.ready(function() {
if (StackExchange.options.isMobile) return;
$('.dupe-hammer-message-hover:not(.hover-bound)').each(function() {
var $hover = $(this).addClass('hover-bound'),
$msg = $hover.siblings('.dupe-hammer-message');
$hover.hover(
function() {
$hover.showInfoMessage('', {
messageElement: $msg.clone().show(),
transient: false,
position: { my: 'bottom left', at: 'top center', offsetTop: -7 },
dismissable: false,
relativeToBody: true
});
},
function() {
StackExchange.helpers.removeMessages();
}
);
});
});
Nov 19 '18 at 15:26
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
1
Isn't that endlessly recursive? My function takesXand returns a function that takesXand returns a function that takesXand returns a function that takesX...
– Rotem
Nov 19 '18 at 15:14
Seems to me you're making this harder than it is. Depending on what you want to do, functors or function pointers are probably appropriate.
– Andrew Henle
Nov 19 '18 at 15:16
The goal is innocent and simple: A really simple state machine. The "state" was going to be represented by a function. Calling the function would return the next "state" which would just be another function. Maybe it's overly clever.
– Michael Gantz
Nov 19 '18 at 15:18
@SergeyA - It doesn't have to return itself, it could return a different function that matches the signature.
– Michael Gantz
Nov 19 '18 at 15:20
This is so similar to a C problem of function returning itself.
– Kamil Cuk
Nov 19 '18 at 15:27
|
show 1 more comment
This question already has an answer here:
Recursive typedef function definition : std::function returning its own type
3 answers
Let's start with a simple typedef of a function:
typedef std::function<uint32_t(SomeStruct *)> HandlerFunction;
Here we have a function that returns a uint32_t and takes a pointer to SomeStruct.
What I would like to do is modify this function so it returns a type of itself, something like this:
typedef std::function<HandlerFunction(SomeStruct *)> HandlerFunction;
Obviously that won't compile, but it represents the end goal I'm trying to achieve.
c++
asked Nov 19 '18 at 15:12
Michael Gantz
6525
This question already has an answer here:
Recursive typedef function definition : std::function returning its own type
3 answers
Let's start with a simple typedef of a function:
typedef std::function<uint32_t(SomeStruct *)> HandlerFunction;
Here we have a function that returns a uint32_t and takes a pointer to SomeStruct.
What I would like to do is modify this function so it returns a type of itself, something like this:
typedef std::function<HandlerFunction(SomeStruct *)> HandlerFunction;
Obviously that won't compile, but it represents the end goal I'm trying to achieve.
This question already has an answer here:
Recursive typedef function definition : std::function returning its own type
3 answers
c++
c++
asked Nov 19 '18 at 15:12
Michael Gantz
6525
asked Nov 19 '18 at 15:12
Michael Gantz
6525
asked Nov 19 '18 at 15:12
Michael Gantz
6525
asked Nov 19 '18 at 15:12
Michael Gantz
6525
asked Nov 19 '18 at 15:12
Michael Gantz
6525
6525
marked as duplicate by SergeyA c++
Users with the c++ badge can single-handedly close c++ questions as duplicates and reopen them as needed.
StackExchange.ready(function() {
if (StackExchange.options.isMobile) return;
$('.dupe-hammer-message-hover:not(.hover-bound)').each(function() {
var $hover = $(this).addClass('hover-bound'),
$msg = $hover.siblings('.dupe-hammer-message');
$hover.hover(
function() {
$hover.showInfoMessage('', {
messageElement: $msg.clone().show(),
transient: false,
position: { my: 'bottom left', at: 'top center', offsetTop: -7 },
dismissable: false,
relativeToBody: true
});
},
function() {
StackExchange.helpers.removeMessages();
}
);
});
});
Nov 19 '18 at 15:26
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
marked as duplicate by SergeyA c++
Users with the c++ badge can single-handedly close c++ questions as duplicates and reopen them as needed.
StackExchange.ready(function() {
if (StackExchange.options.isMobile) return;
$('.dupe-hammer-message-hover:not(.hover-bound)').each(function() {
var $hover = $(this).addClass('hover-bound'),
$msg = $hover.siblings('.dupe-hammer-message');
$hover.hover(
function() {
$hover.showInfoMessage('', {
messageElement: $msg.clone().show(),
transient: false,
position: { my: 'bottom left', at: 'top center', offsetTop: -7 },
dismissable: false,
relativeToBody: true
});
},
function() {
StackExchange.helpers.removeMessages();
}
);
});
});
Nov 19 '18 at 15:26
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
1
Isn't that endlessly recursive? My function takesXand returns a function that takesXand returns a function that takesXand returns a function that takesX...
– Rotem
Nov 19 '18 at 15:14
Seems to me you're making this harder than it is. Depending on what you want to do, functors or function pointers are probably appropriate.
– Andrew Henle
Nov 19 '18 at 15:16
The goal is innocent and simple: A really simple state machine. The "state" was going to be represented by a function. Calling the function would return the next "state" which would just be another function. Maybe it's overly clever.
– Michael Gantz
Nov 19 '18 at 15:18
@SergeyA - It doesn't have to return itself, it could return a different function that matches the signature.
– Michael Gantz
Nov 19 '18 at 15:20
This is so similar to a C problem of function returning itself.
– Kamil Cuk
Nov 19 '18 at 15:27
|
show 1 more comment
1
Isn't that endlessly recursive? My function takesXand returns a function that takesXand returns a function that takesXand returns a function that takesX...
– Rotem
Nov 19 '18 at 15:14
Seems to me you're making this harder than it is. Depending on what you want to do, functors or function pointers are probably appropriate.
– Andrew Henle
Nov 19 '18 at 15:16
The goal is innocent and simple: A really simple state machine. The "state" was going to be represented by a function. Calling the function would return the next "state" which would just be another function. Maybe it's overly clever.
– Michael Gantz
Nov 19 '18 at 15:18
@SergeyA - It doesn't have to return itself, it could return a different function that matches the signature.
– Michael Gantz
Nov 19 '18 at 15:20
This is so similar to a C problem of function returning itself.
– Kamil Cuk
Nov 19 '18 at 15:27
1
1
Isn't that endlessly recursive? My function takes
X and returns a function that takes X and returns a function that takes X and returns a function that takes X...– Rotem
Nov 19 '18 at 15:14
Isn't that endlessly recursive? My function takes
X and returns a function that takes X and returns a function that takes X and returns a function that takes X...– Rotem
Nov 19 '18 at 15:14
Seems to me you're making this harder than it is. Depending on what you want to do, functors or function pointers are probably appropriate.
– Andrew Henle
Nov 19 '18 at 15:16
Seems to me you're making this harder than it is. Depending on what you want to do, functors or function pointers are probably appropriate.
– Andrew Henle
Nov 19 '18 at 15:16
The goal is innocent and simple: A really simple state machine. The "state" was going to be represented by a function. Calling the function would return the next "state" which would just be another function. Maybe it's overly clever.
– Michael Gantz
Nov 19 '18 at 15:18
The goal is innocent and simple: A really simple state machine. The "state" was going to be represented by a function. Calling the function would return the next "state" which would just be another function. Maybe it's overly clever.
– Michael Gantz
Nov 19 '18 at 15:18
@SergeyA - It doesn't have to return itself, it could return a different function that matches the signature.
– Michael Gantz
Nov 19 '18 at 15:20
@SergeyA - It doesn't have to return itself, it could return a different function that matches the signature.
– Michael Gantz
Nov 19 '18 at 15:20
This is so similar to a C problem of function returning itself.
– Kamil Cuk
Nov 19 '18 at 15:27
This is so similar to a C problem of function returning itself.
– Kamil Cuk
Nov 19 '18 at 15:27
|
show 1 more comment
2 Answers
2
active
oldest
votes
I don't see how this could be achieved with std::function.
However, this code (using a functor instead) compiles and runs in Visual Studio 2017:
struct SomeStruct {};
struct Func
{
Func operator()(SomeStruct*) { return *this; }
};
int main()
{
Func f;
Func f2 = f(nullptr);
}
answered Nov 19 '18 at 15:27
sebrockm
769214
add a comment |
Unfortunately it is not possible. However, if your goal is to implement a finite state machine boost::statechart may help you
answered Nov 19 '18 at 15:25
bogdan tudose
867
add a comment |
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
I don't see how this could be achieved with std::function.
However, this code (using a functor instead) compiles and runs in Visual Studio 2017:
struct SomeStruct {};
struct Func
{
Func operator()(SomeStruct*) { return *this; }
};
int main()
{
Func f;
Func f2 = f(nullptr);
}
answered Nov 19 '18 at 15:27
sebrockm
769214
add a comment |
I don't see how this could be achieved with std::function.
However, this code (using a functor instead) compiles and runs in Visual Studio 2017:
struct SomeStruct {};
struct Func
{
Func operator()(SomeStruct*) { return *this; }
};
int main()
{
Func f;
Func f2 = f(nullptr);
}
answered Nov 19 '18 at 15:27
sebrockm
769214
add a comment |
I don't see how this could be achieved with std::function.
However, this code (using a functor instead) compiles and runs in Visual Studio 2017:
struct SomeStruct {};
struct Func
{
Func operator()(SomeStruct*) { return *this; }
};
int main()
{
Func f;
Func f2 = f(nullptr);
}
answered Nov 19 '18 at 15:27
sebrockm
769214
I don't see how this could be achieved with std::function.
However, this code (using a functor instead) compiles and runs in Visual Studio 2017:
struct SomeStruct {};
struct Func
{
Func operator()(SomeStruct*) { return *this; }
};
int main()
{
Func f;
Func f2 = f(nullptr);
}
answered Nov 19 '18 at 15:27
sebrockm
769214
answered Nov 19 '18 at 15:27
sebrockm
769214
answered Nov 19 '18 at 15:27
sebrockm
769214
answered Nov 19 '18 at 15:27
sebrockm
769214
769214
add a comment |
add a comment |
Unfortunately it is not possible. However, if your goal is to implement a finite state machine boost::statechart may help you
answered Nov 19 '18 at 15:25
bogdan tudose
867
add a comment |
Unfortunately it is not possible. However, if your goal is to implement a finite state machine boost::statechart may help you
answered Nov 19 '18 at 15:25
bogdan tudose
867
add a comment |
Unfortunately it is not possible. However, if your goal is to implement a finite state machine boost::statechart may help you
answered Nov 19 '18 at 15:25
bogdan tudose
867
Unfortunately it is not possible. However, if your goal is to implement a finite state machine boost::statechart may help you
answered Nov 19 '18 at 15:25
bogdan tudose
867
answered Nov 19 '18 at 15:25
bogdan tudose
867
answered Nov 19 '18 at 15:25
bogdan tudose
867
answered Nov 19 '18 at 15:25
bogdan tudose
867
867
add a comment |
add a comment |
1
Isn't that endlessly recursive? My function takes
Xand returns a function that takesXand returns a function that takesXand returns a function that takesX...– Rotem
Nov 19 '18 at 15:14
Seems to me you're making this harder than it is. Depending on what you want to do, functors or function pointers are probably appropriate.
– Andrew Henle
Nov 19 '18 at 15:16
The goal is innocent and simple: A really simple state machine. The "state" was going to be represented by a function. Calling the function would return the next "state" which would just be another function. Maybe it's overly clever.
– Michael Gantz
Nov 19 '18 at 15:18
@SergeyA - It doesn't have to return itself, it could return a different function that matches the signature.
– Michael Gantz
Nov 19 '18 at 15:20
This is so similar to a C problem of function returning itself.
– Kamil Cuk
Nov 19 '18 at 15:27