Mirror of forum.nim-lang.org

7473 :: Traits or macros for inspecting proc/lambda/functor type

• filcuc (orginal) [2021-02-05T00:08:46+01:00] view original

  Are there macros/traits for inspecting a proc function pointer type?

  Examples: 1) Being able to iterate on each argument type

  
  template foo(f: proc(int)) =
     for typ in f.argsTypes:
         // do something with the type
  Run

  2. Having the number of arguments
  3. Having the return type

---

• ElegantBeef (orginal) [2021-02-05T00:14:37+01:00] view original

  Macros are capable of getting the arguement/return type. The following code will echo out the following ast.

  import macros
  macro test(a: typed): untyped =
    echo a.getImpl().treeRepr
  let a = proc(i: int): float = 1.0
  a.test
  Run

  
  IdentDefs
    Sym "a"
    Empty
    Lambda
      Sym ":anonymous"
      Empty
      Empty
      FormalParams
        Sym "float"
        IdentDefs
          Sym "i"
          Sym "int"
          Empty
      Empty
      Empty
      Asgn
        Sym "result"
        FloatLit 1.0
      Sym "result"
  Run

  Which should let you generate all the logic you want to.

---