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1993 :: Another one question about c2nim

• karatin (orginal) [2016-01-31T11:06:28+01:00] view original

  Is it possible to convert c code:

  #define TO__STR(n) #n
  #define TO_STR(n) H2O_TO__STR(n)
  
  #define STRLIT(s) (s), sizeof(s) - 1
  Run

  into Nim code? If yes, then how to do it?

  Arguments in that macros are

  const char *
  Run

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• Stefan_Salewski (orginal) [2016-01-31T12:28:33+01:00] view original

  The stringify C macro is not supported currently by c2nim. I tried six months ago something with my own Nim stringify macro like:

  macro stringify*(n: expr): string =
    result = newNimNode(nnkStmtList, n)
    result.add(toStrLit(n))
  Run

  with that macro something like

  template TO_STR(n): string = stringify(n)
  Run

  may work. Can not really remember details, I was working on the strange gobject macros to get GTK3 application10 to work, but my macro skills are bad. You have to import macros, and with that macro something like this works:

  echo(TO_STR(1 + 2)) # gives 1 + 2
  Run

  For the other two defines, c2nim may give you

  template TO_STR*(n: expr): expr =
    H2O_TO__STR(n)
  
  template STRLIT*(s: expr): expr =
    (s)
    sizeof((s)) - 1
  Run

  You have to see how useful that is. Two underscores may be a problem for Nim, you may have to replace that.

  For the second line something like

  const TO_STR = H2O_TO__STR
  Run

  may be a solution, but care for the two underscores. That is an proc alias, you have to check if that is what is really desired.

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• karatin (orginal) [2016-01-31T14:01:40+01:00] view original

  Thanks for your reply.

  #define STRLIT(s) (s), sizeof(s) - 1
  Run

  That macro is used to make parameters to functions.

  For example:

  vec_init(STRLIT("localhost"))
  Run

  will produce

  vec_init("localhost",9)
  Run

  How to make it in Nim? Please.

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• Stefan_Salewski (orginal) [2016-01-31T14:59:47+01:00] view original

  Can not help you, sorry. Basically something like

  template STRLIT(s: static[string]): expr =
    s, sizeof(s) - 1
  Run

  But that does snot compile. Maybe a macro is required, so we have to wait for an answer of the experts.

  Or you may do a plain text substitution of course, maybe replace "STRLIT(s)" with "s, sizeof(s) - 1"

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• karatin (orginal) [2016-01-31T16:32:26+01:00] view original

  Wrong:

  
  prog.nim(2, 4) Error: invalid indentation
  Run

  In Nim c code sizeof(s) is len s for strings

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• OderWat (orginal) [2016-01-31T18:07:16+01:00] view original

  AFAIK you can't create 2 parameters from 1 with a template anyway.

  Something like this will work but is probably not of any help:

  template STRLIT(s: static[string]): expr =  (s, s.len - 1)
  
  proc test(s: string, n: int) =
    echo s & " (" & $n & ")"
  
  proc test(x: tuple[s: string, n: int]) = test(x.s, x.n)
  
  const a = "test"
  test(STRLIT(a))
  Run

  What you can do is something like what we do for the wxcnim module to "fake" the possibility to have a proc which accepts special parameters, but for this you need to wrap the whole call with a helper macro:

  import macros
  
  #proc point*(x, y: int) = discard
  #proc rect*(a, b, c, d: int) = discard
  
  template unpackingArgs(nimname,extname) =
    macro nimname*(n: varargs[untyped]): expr =
      var call = newCall(!astToStr(extname))
      for x in n.children:
        var unpack = false
        if x.kind in nnkCallKinds:
          case $x[0]
          of "point":
            expectLen(x, 3)
            unpack = true
          of "rect":
            expectLen(x, 5)
            unpack = true
          else: discard
        
        if unpack:
          for i in 1..<x.len:
            call.add(x[i])
        else:
          call.add(x)
      
      result = newStmtList(call)
  
  proc takesSeven(left,top,width,height,col,x,y: int) =
    echo $left & " " & $top & " / " & $width & " " & $height
    echo col
    echo $x & " " & $y
  
  # create a version which supports "define style parameters"
  unpackingArgs(takesStuff, takesSeven)
  
  echo "Takes Seven:"
  takesSeven(1,2,3,4,5,6,7)
  
  echo "Takes Stuff 1 (OK):"
  takesStuff(rect(1,2,3,4),5,point(6,7))
  
  echo "Takes Stuff 2 (MEH):"
  takesStuff(rect(1,2,3,4),point(5,6),7)
  
  Run

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