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8357 :: Nested macro expansion order

• apardes (orginal) [2021-08-23T20:29:16+02:00] view original

  Is there any way for a macro to expand nested macros during its evaluation?

  For example, if there are macros foo(x) and bar() and we write:

  foo(bar())

  Is it possible for foo to access the AST which would be generated by bar?

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• haxscramper (orginal) [2021-08-23T20:40:08+02:00] view original

  If foo has typed argument then bar() is evaluated first and then resulting AST is passed as argument. Note that bar's output AST would be fully expanded before being passed to foo

  macro bar(): untyped = newLit("bar-expanded")
  
  macro foo(arg: typed) = echo arg.treeRepr()
  
  foo(bar())
  Run

  
  StrLit "bar-expanded"
  Run

  If foo has untyped argument then it would simply accept bar()

  macro bar(): untyped = newLit("bar-expanded")
  
  macro foo(arg: untyped) = echo arg.treeRepr()
  
  foo(bar())
  Run

  
  
  Call
    Ident "bar"
  Run

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• nimnam (orginal) [2023-03-10T21:28:28+01:00] view original

  Can you use a macro in a macro? like

  macro sqr(x: typed):

  quote: x * x

  macro do():

  quote sqr(2)

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• auxym (orginal) [2023-03-10T22:57:45+01:00] view original

  Yes, macros are expanded "outside in". That is, the outermost macro is evaluating. Then, if the resulting AST contains more macros (or templates), they are evaluated, and the process continues like this recursively.

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