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7497 :: macros - backquote

• mantielero (orginal) [2021-02-11T20:07:03+01:00] view original

  I am trying to write a macro:

  macro genModelInstance*( NUMBER_OF_REALS, NUMBER_OF_INTEGERS,
                 NUMBER_OF_BOOLEANS, NUMBER_OF_STRINGS,
                 NUMBER_OF_STATES, NUMBER_OF_EVENT_INDICATORS: static[int]): untyped =
    #echo NUMBER_OF_REALS # just an int (7), not ``NimNode``
    result = quote do:
        type
          ModelInstance* = ref object
              r*:          array[`NUMBER_OF_REALS`, fmi2Real]
              i*:          array[`NUMBER_OF_INTEGERS`, fmi2Integer]
              b*:          array[`NUMBER_OF_BOOLEANS`, fmi2Boolean]
              s*:          array[`NUMBER_OF_STRINGS`, fmi2String]
              isPositive*: array[`NUMBER_OF_EVENT_INDICATORS`, fmi2Boolean]
              time*: fmi2Real
              instanceName*: fmi2String
              `type`*: fmi2Type
         ....
  Run

  The question is about the last line. I want to name the field as type which requires backquotes: `type` so that it is not confused with a type definition. But the backquotes in the macro refer to macro arguments.

  Is there a way to fix this?

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• shirleyquirk (orginal) [2021-02-12T00:02:30+01:00] view original

  if you dumpTree the type you want, it'll show you the AST you need to generate. You might not be able to use quote do for that bit but you can always construct the ast manually.

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• Araq (orginal) [2021-02-12T08:22:30+01:00] view original

  And please don't scream NUMBER_OF_REALS, it's really not that terrible.

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• PMunch (orginal) [2021-02-12T09:53:58+01:00] view original

  This is a bit tricky, looking at the output from dumpAstGen you can see how to generate a node like that. Easiest is probably to create it as a variable and then insert that: var typeNode = nnkAccQuoted.newTree(newIdentNode("type"))`and then simply use ` `typeNode ` in your expansion.

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• mantielero (orginal) [2021-02-12T15:28:45+01:00] view original

  I am following that approach:

  macro genModelInstance*( NUMBER_OF_REALS, NUMBER_OF_INTEGERS,
                 NUMBER_OF_BOOLEANS, NUMBER_OF_STRINGS,
                 NUMBER_OF_STATES, NUMBER_OF_EVENT_INDICATORS: static[int]): untyped =
    let modelInstance = nnkPostfix.newTree(
                          newIdentNode("*"),
                          newIdentNode("ModelInstance")
                        )
    
    let mytype = nnkPostfix.newTree(
                   newIdentNode("*"),
                   nnkAccQuoted.newTree( newIdentNode("type") )
                 )
    
    result = quote do:
        type
          `modelInstance` = ref object
              r*:          array[`NUMBER_OF_REALS`, fmi2Real]
              i*:          array[`NUMBER_OF_INTEGERS`, fmi2Integer]
              b*:          array[`NUMBER_OF_BOOLEANS`, fmi2Boolean]
              s*:          array[`NUMBER_OF_STRINGS`, fmi2String]
              isPositive*: array[`NUMBER_OF_EVENT_INDICATORS`, fmi2Boolean]
              time*: fmi2Real
              instanceName*: fmi2String
              `mytype`: fmi2Type
              ...
  Run

  But for some reason I am getting:

  type
    ModelInstance = ref object
      r*: array[3, fmi2Real]
      i*: array[2, fmi2Integer]
      b*: array[1, fmi2Boolean]
      s*: array[4, fmi2String]
      isPositive*: array[6, fmi2Boolean]
      time*: fmi2Real
      instanceName*: fmi2String
      `type`*: fmi2Type
  ...
  Run

  where I get ModelInstance instead of ModelInstance*.

  @arak you are absolutely right. I need to reorganize the whole code and to get closer to the style guide. It is just copied from the original C code.

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• mantielero (orginal) [2021-02-12T15:53:00+01:00] view original

  My bad. I see that I have something wrong elsewhere.

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