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11148 :: Artificial AST

• sls1005 (orginal) [2024-03-05T08:18:13+01:00] view original

  What will happen if the AST generated by a macro is obviously artificial or unnatural (that will never come from the code parser)?

  For example,

  
  Infix
    Ident "*"
    Infix
      Ident "+"
      IntLit 1
      IntLit 2
    IntLit 3
  Run

  Is it still vaild?

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• Araq (orginal) [2024-03-05T08:40:52+01:00] view original

  Why wouldn't your example be valid? The compiler checks the AST after macro expansion, it can reject it and produce an error message.

  To be honest, I doubt I understood your question.

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• sls1005 (orginal) [2024-03-05T09:18:14+01:00] view original

  Because

  1 + 2 * 3
  Run

  will become

  
  Infix
    Ident "+"
    IntLit 1
    Infix
      Ident "*"
      IntLit 2
      IntLit 3
  Run

  or alike, while

  (1 + 2) * 3
  Run

  becomes

  
  Infix
    Ident "*"
    Par
      Infix
        Ident "+"
        IntLit 1
        IntLit 2
    IntLit 3
  Run

  or alike.

  There's no way to form the AST I provided in the first post, except by using a macro to generate it artificially, so I said it's "artificial" or "unnatural." But I'm not sure if it's wrong.

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• janAkali (orginal) [2024-03-05T14:17:40+01:00] view original

  Why not try it? Here's example implementation:

  import std/[macros]
  
  macro foo(): untyped =
    result = newStmtList(
      infix(
        newLit(1),
        "*",
        infix(
          newLit(2),
          "+",
          newLit(3)
        )
      )
    )
    echo result.repr # this line will print the code generated by a macro at compile time
  
  echo foo()
  Run

  Here's the code generated by the macro:

  
  1 * (2 + 3)
  Run

  Output is obviously - 5

  I hope this answers your question.

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