Struct with template variables in C

Question

I m playing around with templates  I m not trying to reinvent the std  vector  I m trying to get a grasp of templateting in C     Can I do the following   template  lt typename T gt  typedef struct    size t x    T  ary   array    What I m trying to do is a basic templated version of   typedef struct    size t x    int  ary   iArray    It looks like it s working if I use a class instead of struct  so is it not possible with typedef structs

User · Answer

The Standard says  at 14 3  For the non-standard folks  the names following a class definition body  or the type in a declaration in general  are  declarators       In a template-declaration  explicit specialization  or explicit instantiation the init-declarator-list in the dec-laration shall contain at most one declarator  When such a declaration is used to declare a class template  no declarator is permitted    Do it like Andrey shows

User · Answer

You can template a struct as well as a class  However you can t template a typedef  So template lt typename T gt  struct array        works  but template lt typename T gt  typedef struct       array  does not  Note that there is no need for the typedef trick in C    you can use structs without the struct modifier just fine in C

User · Answer

The problem is you can t template a typedef  also there is no need to typedef structs in C     The following will do what you need  template  lt typename T gt   struct array      size t x     T  ary

User · Answer

You don t need to do an explicit typedef for classes and structs  What do you need the typedef for  Further  the typedef after a template lt     gt  is syntactically wrong  Simply use   template  lt class T gt  struct array     size t x    T  ary

User · Answer

From the other answers  the problem is that you re templating a typedef  The only  way  to do this is to use a templated class  ie  basic template metaprogramming   template lt class T gt  class vector Typedefs         typedef   struct array     The typedef isn t necessary         size t x           T  ary                  Any other templated typedefs you need  Think of the templated class like something        between a function and namespace       An advantage is  template lt  gt  class vector Typedefs lt bool gt        struct array             Special behavior for the binary array

User · Answer

Looks like  monkeyking is trying it to make it more obvious code as shown below template  lt typename T gt   struct Array      size t x     T  ary       typedef Array lt int gt  iArray  typedef Array lt float gt  fArray

User · Answer

template  lt typename T gt  struct array     size t x    T  ary

User · Answer

The syntax is wrong  The typedef should be removed

[c++] Struct with template variables in C++

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