Currying template with parameter from another template
I have class Foo, which has two template parameters, A and B:
template<typename A, typename B>
struct Foo {};
Also I have class Base, which has one template template parameter:
template<template<typename B> typename Foo>
struct Base {};
I want to write class Derived assuming the following:
Derivedhas one template parameter (A)
Derivedextends classBase
Derivedpasses as template parameter to classBaseclassFoo, but with one parameter "currying" (A)
How can I do this?
Here is my (not working) solution:
template<template<typename B> typename Foo>
struct Base {};
template<typename A, typename B>
struct Foo {};
template<template<typename A, typename B> typename Foo, typename A>
struct BindFirst {
template<typename B>
using Result = Foo<A, B>;
};
template<typename A>
struct Derived : Base<
// error is here
typename BindFirst<Foo, A>::Result
> {};
Which gives me error:
template argument for template template parameter must be a class template or type alias template
c++ templates metaprogramming currying
asked Nov 12 '18 at 22:09
dirariadiraria
6901625
add a comment |
I have class Foo, which has two template parameters, A and B:
template<typename A, typename B>
struct Foo {};
Also I have class Base, which has one template template parameter:
template<template<typename B> typename Foo>
struct Base {};
I want to write class Derived assuming the following:
Derivedhas one template parameter (A)
Derivedextends classBase
Derivedpasses as template parameter to classBaseclassFoo, but with one parameter "currying" (A)
How can I do this?
Here is my (not working) solution:
template<template<typename B> typename Foo>
struct Base {};
template<typename A, typename B>
struct Foo {};
template<template<typename A, typename B> typename Foo, typename A>
struct BindFirst {
template<typename B>
using Result = Foo<A, B>;
};
template<typename A>
struct Derived : Base<
// error is here
typename BindFirst<Foo, A>::Result
> {};
Which gives me error:
template argument for template template parameter must be a class template or type alias template
c++ templates metaprogramming currying
asked Nov 12 '18 at 22:09
dirariadiraria
6901625
2
BindFirst<Foo, A>::template Result(notypename, it's a template).
– Henri Menke
Nov 12 '18 at 22:19
1
Live demo: gcc.godbolt.org/z/RpsRbT
– melpomene
Nov 12 '18 at 22:21
add a comment |
I have class Foo, which has two template parameters, A and B:
template<typename A, typename B>
struct Foo {};
Also I have class Base, which has one template template parameter:
template<template<typename B> typename Foo>
struct Base {};
I want to write class Derived assuming the following:
Derivedhas one template parameter (A)
Derivedextends classBase
Derivedpasses as template parameter to classBaseclassFoo, but with one parameter "currying" (A)
How can I do this?
Here is my (not working) solution:
template<template<typename B> typename Foo>
struct Base {};
template<typename A, typename B>
struct Foo {};
template<template<typename A, typename B> typename Foo, typename A>
struct BindFirst {
template<typename B>
using Result = Foo<A, B>;
};
template<typename A>
struct Derived : Base<
// error is here
typename BindFirst<Foo, A>::Result
> {};
Which gives me error:
template argument for template template parameter must be a class template or type alias template
c++ templates metaprogramming currying
asked Nov 12 '18 at 22:09
dirariadiraria
6901625
I have class Foo, which has two template parameters, A and B:
template<typename A, typename B>
struct Foo {};
Also I have class Base, which has one template template parameter:
template<template<typename B> typename Foo>
struct Base {};
I want to write class Derived assuming the following:
Derivedhas one template parameter (A)
Derivedextends classBase
Derivedpasses as template parameter to classBaseclassFoo, but with one parameter "currying" (A)
How can I do this?
Here is my (not working) solution:
template<template<typename B> typename Foo>
struct Base {};
template<typename A, typename B>
struct Foo {};
template<template<typename A, typename B> typename Foo, typename A>
struct BindFirst {
template<typename B>
using Result = Foo<A, B>;
};
template<typename A>
struct Derived : Base<
// error is here
typename BindFirst<Foo, A>::Result
> {};
Which gives me error:
template argument for template template parameter must be a class template or type alias template
c++ templates metaprogramming currying
c++ templates metaprogramming currying
asked Nov 12 '18 at 22:09
dirariadiraria
6901625
asked Nov 12 '18 at 22:09
dirariadiraria
6901625
edited Nov 12 '18 at 22:16
diraria
asked Nov 12 '18 at 22:09
dirariadiraria
6901625
asked Nov 12 '18 at 22:09
dirariadiraria
6901625
asked Nov 12 '18 at 22:09
dirariadiraria
6901625
6901625
2
BindFirst<Foo, A>::template Result(notypename, it's a template).
– Henri Menke
Nov 12 '18 at 22:19
1
Live demo: gcc.godbolt.org/z/RpsRbT
– melpomene
Nov 12 '18 at 22:21
add a comment |
2
BindFirst<Foo, A>::template Result(notypename, it's a template).
– Henri Menke
Nov 12 '18 at 22:19
1
Live demo: gcc.godbolt.org/z/RpsRbT
– melpomene
Nov 12 '18 at 22:21
2
2
BindFirst<Foo, A>::template Result (no typename, it's a template).– Henri Menke
Nov 12 '18 at 22:19
BindFirst<Foo, A>::template Result (no typename, it's a template).– Henri Menke
Nov 12 '18 at 22:19
1
1
Live demo: gcc.godbolt.org/z/RpsRbT
– melpomene
Nov 12 '18 at 22:21
Live demo: gcc.godbolt.org/z/RpsRbT
– melpomene
Nov 12 '18 at 22:21
add a comment |
1 Answer
1
active
oldest
votes
The template Base expects a template as the first parameter but you attempt to pass a dependent type (indicated by typename), hence the error message. Moreover, the nested alias Result inside BindFirst is a template and therefore would require a template parameter for use with typename. So instead of
typename BindFirst<Foo, A>::Result
you have to tell the compiler that Result is in fact a template, using
BindFirst<Foo, A>::template Result
Live example
answered Nov 12 '18 at 22:24
Henri MenkeHenri Menke
7,54011327
add a comment |
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1 Answer
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active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
The template Base expects a template as the first parameter but you attempt to pass a dependent type (indicated by typename), hence the error message. Moreover, the nested alias Result inside BindFirst is a template and therefore would require a template parameter for use with typename. So instead of
typename BindFirst<Foo, A>::Result
you have to tell the compiler that Result is in fact a template, using
BindFirst<Foo, A>::template Result
Live example
answered Nov 12 '18 at 22:24
Henri MenkeHenri Menke
7,54011327
add a comment |
The template Base expects a template as the first parameter but you attempt to pass a dependent type (indicated by typename), hence the error message. Moreover, the nested alias Result inside BindFirst is a template and therefore would require a template parameter for use with typename. So instead of
typename BindFirst<Foo, A>::Result
you have to tell the compiler that Result is in fact a template, using
BindFirst<Foo, A>::template Result
Live example
answered Nov 12 '18 at 22:24
Henri MenkeHenri Menke
7,54011327
add a comment |
The template Base expects a template as the first parameter but you attempt to pass a dependent type (indicated by typename), hence the error message. Moreover, the nested alias Result inside BindFirst is a template and therefore would require a template parameter for use with typename. So instead of
typename BindFirst<Foo, A>::Result
you have to tell the compiler that Result is in fact a template, using
BindFirst<Foo, A>::template Result
Live example
answered Nov 12 '18 at 22:24
Henri MenkeHenri Menke
7,54011327
The template Base expects a template as the first parameter but you attempt to pass a dependent type (indicated by typename), hence the error message. Moreover, the nested alias Result inside BindFirst is a template and therefore would require a template parameter for use with typename. So instead of
typename BindFirst<Foo, A>::Result
you have to tell the compiler that Result is in fact a template, using
BindFirst<Foo, A>::template Result
Live example
answered Nov 12 '18 at 22:24
Henri MenkeHenri Menke
7,54011327
answered Nov 12 '18 at 22:24
Henri MenkeHenri Menke
7,54011327
answered Nov 12 '18 at 22:24
Henri MenkeHenri Menke
7,54011327
answered Nov 12 '18 at 22:24
Henri MenkeHenri Menke
7,54011327
7,54011327
add a comment |
add a comment |
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2
BindFirst<Foo, A>::template Result(notypename, it's a template).– Henri Menke
Nov 12 '18 at 22:19
1
Live demo: gcc.godbolt.org/z/RpsRbT
– melpomene
Nov 12 '18 at 22:21