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5392 :: Possible to use identifier construction to call proc by name (string)?

• geohuz (orginal) [2019-10-24T13:06:32+02:00] view original

  Just like in python/js, we have the following proc:

  proc newAuthMessage() =
   ...
  
  proc newSubscribeMessage() =
   ...
  Run

  and I want to call these procedures dynamically, so we have string "Auth" , "Subscribe", and now I need concatenate the string and call them. I tried with template but no luck.

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• mratsim (orginal) [2019-10-24T13:17:17+02:00] view original

  proc names must be known at compile time. Use closures instead.

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• Araq (orginal) [2019-10-24T13:36:43+02:00] view original

  To expand on what mratsim said, you need to use an explicit string->proc lookup table. This table can be filled via a macro.

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• geohuz (orginal) [2019-10-24T16:43:29+02:00] view original

  I tried to write the code (by following the manual):

  import macros
  import tables
  
  var nameToProc {.compileTime.} = newTable[string, proc(): string {.nimcall.}]()
  
  macro registerProc(p: untyped): untyped =
    result = newTree(nnkStmtList, p)
    
    echo repr(p[0])
    let procName = p[0]
    let procNameAsStr = $p[0]
    
    result.add quote do:
      nameToProc.add(`procNameAsStr`, `procName`)
  
  
  proc foo: string {.registerProc.} = "foo"
  proc bar: string {.registerProc.} = "bar"
  proc baz: string {.registerProc.} = "baz"
  
  
  doAssert nameToProc["foo"]() == "foo"
  Run

  But I get the following error:

  
  Error: unhandled exception: key not found: foo [KeyError]
  Run

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• geohuz (orginal) [2019-10-24T17:07:21+02:00] view original

  Ok, I tried to remove compileTime pragma and it runs successfully, hope somebody can give me explanation.

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• demotomohiro (orginal) [2019-10-24T19:28:35+02:00] view original

  I don't think nameToProc can be a compileTime variable because an address of procedure cannot be determined at compile time.

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• Krux02 (orginal) [2019-10-25T09:44:32+02:00] view original

  This is my solution to call functions by name: https://github.com/krux02/opengl-sandbox/blob/master/examples/console.nim

  This example in this project does not have any dependentcies of that project itself, it should just work stand alone.

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• Araq (orginal) [2019-10-25T09:48:49+02:00] view original

  I'm pretty sure this a regression, https://github.com/nim-lang/Nim/issues/12516

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