Clash Royale CLAN TAG#URR8PPP

Macro for template definitions

I have a problem with alias template, because I have a code which must be compatible with VS 2012, which does not support alias template.

Let's say I have an alias template like:

template<typename A, typename B> using foo = bar<A,B>;


Then it would be very convenient to be able to do something like:

#ifdef NO_ALIAS_TEMPLATE_AVAILABLE
#define foo<x,y> bar<x,y>
#else
template<typename A, typename B> using foo = bar<A,B>;
#endif


However the best I can do is

#define foo(x,y) bar<x,y>


And I don't want to replace all template specializations in all my code by round brackets, for code readability.

Is there any way to have a macro with delimiters <> for its argument? Or is there no simple solution to my problem? If not, how to implement a strict equivalence to alias template?

<>

2 Answers
2

No, the preprocessor cannot use <> to delimit macro arguments.

<>

You can emulate an alias template with a class template:

template <typename A, typename B>
struct foo
typedef bar<A, B> type;
;

// Usage: foo<A, B>::type
// Generic context: typename foo<A, B>::type


Demo

This would make its usage less nice, but that's unavoidable.

The following simpler solution works for me.

#ifdef NO_ALIAS_TEMPLATE_AVAILABLE
#define foo bar
#else
template<typename A, typename B> using foo = bar<A,B>;
#endif


Given

template <typename A, typename B> struct bar ;


the following lines work fine.

foo<int, double> f; // Ok.
bar<int, double> b; // Ok.


foo

#define MY_LIBRARY_FOO ::fully::qualified::bar

template <typename A, typename B> using MY_LIBRARY_FOO = bar<A, B>

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