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1879 :: reconstruct closure

• geezer9 (orginal) [2015-12-16T03:32:14+01:00] view original

  Below is an incorrect attempt to reconstruct the call of a closure using only its raw proc and raw env. This is needed to pass a nim closure as a c callback to the iup module. If I can do that reconstruction, then I can save the nim closure parts as attributes of an iup object and thus (with an appropriate ACTION) use it as a callback.

  proc times(x:int) : proc(y:int):int =   # curry-ed application
      return proc(y:int):int = x*y
  
  var fn = times(6)  # the closure
  echo fn(3)   # it works
  
  var rawP = fn.rawProc()
  var rawE = fn.rawEnv()
  
  echo cast[proc(env:pointer,y:int):int](rawP)(rawE,3)   #  THIS FAILS
  Run

  The error is caught in the c compiler - since cast hides it from nim???

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• jlp765 (orginal) [2015-12-16T06:45:09+01:00] view original

  This doesn't answer your question directly, but is working code for an IUP callback

  
  
  proc toCB(fp: proc): ICallback =
     return cast[ICallback](fp)
  
  var btnFull = button("Full screen","")
  
  proc doFull(ih:PIhandle): cint {.cdecl.} =
      setAttribute(dlg,"FULLSCREEN","YES")
      return IUP_DEFAULT
  
  discard setCallback(btnFull,"ACTION", toCB(doFull))
  Run

  IUP attributes are text, but your callback is a Nim procvar (?).

  I am guessing you are wanting to save the callback as an attribute of an IUP object (which is text), and you will have to convert between that text and a Nim procvar

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• jangko (orginal) [2015-12-16T07:21:13+01:00] view original

  env pointer should be the last param and the callconv should be .nimcall.

  
  type
    abcd = proc(a: int, x:pointer): int {.nimcall.}
  
  echo cast[abcd](rawP)(3, rawE)
  Run

  and the documentation should be clear on this topic, but it is not :)

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