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7543 :: Templates - cannot evaluate at compile time: elems

• mantielero (orginal) [2021-02-21T19:09:05+01:00] view original

  I have a situation similar to the following:

  template subBlock():untyped {.dirty.} =
     #echo elems.len
     const
       b = elems.len
  
  template register(a:int):untyped {.dirty.} =
     elems.add(a)
  
  template mainTemplate(body:untyped):untyped {.dirty.} =
    var
      elems:seq[int]
    
    body
  
  
  
  mainTemplate:
    register(4)
    register(5)
    
    subBlock()
  Run

  I am calling a template named register a number of times (in this example two times). In the template subBlock, it fails saying that elems cannot be evaluated at compile time.

  I need b to be a const.

  Any workaround?

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• SolitudeSF (orginal) [2021-02-21T19:46:32+01:00] view original

  https://play.nim-lang.org/#ix=2Qff

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• mantielero (orginal) [2021-02-21T19:52:56+01:00] view original

  You people are amazing. Now I have to understand the magic and integrate it.

  Thanks a lot.

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• SolitudeSF (orginal) [2021-02-21T20:51:34+01:00] view original

  {.compileTime.} makes var exist at compile time. static blocks evaluate at compile time. badabing.

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• ynfle (orginal) [2021-02-22T00:08:14+01:00] view original

  I'm not sure what you are trying to do but const mean that the value can be computed at compile time and put in the binary. If you are just looking for imutable value use let which can house runtime values as well

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