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7674 :: How can I quote a type with a sequence of strings

• DavidKunz (orginal) [2021-03-21T17:54:38+01:00] view original

  Hi,

  Consider this code:

  
  import macros
  
  type Something = object
    manyStrings: seq[string]
  
  macro MyMacro(): untyped =
    var something = Something()
    return quote do:
      `something`
  
  let x: Something = MyMacro() # type mismatch: got <array[0..-1, empty]> but expected 'seq[string]'
  Run

  see playground

  Does someone know why this won't work?

  It works for objects without seq[string], e.g.

  
  type Something = object
    oneString: string
  Run

  Thanks a lot and best regards, David

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• ynfle (orginal) [2021-03-21T18:26:56+01:00] view original

  Try this: https://play.nim-lang.org/#ix=2TFe

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• DavidKunz (orginal) [2021-03-21T18:36:14+01:00] view original

  Hi @ynfle, thanks a lot!

  However, I'd like to create a sequence of Something in the macro itself (a loop, creating many Something and filling the manyStrings property), then in the quote I only want to return this sequence, like this.

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• DavidKunz (orginal) [2021-03-21T18:38:18+01:00] view original

  Update: Looks like it works when I'm using const instead.

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• shirleyquirk (orginal) [2021-03-21T20:07:50+01:00] view original

  since you're not actually manipulating AST with the macro, you probably just want a static: block or const instead to initialize your somethings

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• ynfle (orginal) [2021-03-21T20:11:53+01:00] view original

  Do you just want to computer something at compile time? You can, alternatively use a static expression. Check out the manual here.

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• DavidKunz (orginal) [2021-03-21T20:47:19+01:00] view original

  Thanks for the hint @ynfle, that looks promising! So many hidden gems in Nim...

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• davidshaner (orginal) [2021-03-27T09:39:19+01:00] view original

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