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9671 :: Importing generic variables

• sls1005 (orginal) [2022-11-28T11:22:52+01:00] view original

  What's the best way to wrap this C++ code:

  template <class T> T my_var;
  Run

  As a proc

  proc myVar[T](): T {.importcpp: "my_var<'0>".}
  
  echo myVar[int]()
  Run

  or a variable?

  type S = distinct string
  const myVar = S("my_var")
  proc `[]`[T](v: typeof(myVar), typ: typedesc[T]): T {.importcpp: "my_var<'0>".}
  
  echo myVar[int]
  Run

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• shirleyquirk (orginal) [2022-11-28T15:43:29+01:00] view original

  how about

  {.emit:"""
  template <typename T>
  constexpr T pi = T(3.1415926535897932385L);
  
  template <typename T>
  const static size_t ALIGN_MASK = 64 / sizeof(T) - 1;
  """.}
  
  proc pi[T](t:typedesc[T]):T{.importcpp:"pi<'1>".}
  proc alignMask[T](t:typedesc[T]):csize_t{.importcpp:"ALIGN_MASK<'1>".}
  
  proc area[T](r:T):T = pi(T) * r * r
  
  echo alignMask(int32)
  
  echo area(3.0'f32)
  Run

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