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916 :: Object initialization problem, I think

• CharlesH (orginal) [2015-02-23T21:04:23+01:00] view original

  I'm trying to learn nim, so I picked what I thought was a simple problem. This is what I've got so far, and I haven't been able to figure out what I'm doing wrong. (The problem's in the last line.):

  type
     Direct   =  enum
        n, e, s, w
     Cell  =  ref   CellObj
     CellObj  =  object
        row   :  0..32
        col   :  0..32
        links :  array[Direct, Cell]
     Grid {.inheritable.} =  object
        rows  :  0..32
        cols  :  0..32
        grid  :  array[0..32, array[0..32, Cell]]
        #Note that size of array must be allocated at compile time
        #  but it can be allocated over a range
  
  proc  newCell(row, col: int8):   Cell  =
     result.row  =  row
     result.col  =  col
  
  proc  newGrid(rows, cols: int8): Grid  =
     result.rows =  rows
     result.cols =  cols
     for   i  in 0..rows:
        for   j  in 0..cols:
           result.grid[i, j]  =  newCell(i, j)
  Run

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• Varriount (orginal) [2015-02-23T21:15:06+01:00] view original

  'Cell' is a reference type. Reference types must be allocated by using the 'new' procedure first. On the first line of 'newCell', add a 'new (result)'.

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• CharlesH (orginal) [2015-02-23T21:25:15+01:00] view original

  I tried that (just now), but the error messages are essentially unchanged:

  grid.nim(27, 20) Error: type mismatch: got (array[0..32, array[0..32, Cell]], int8, int8, Cell)
  but expected one of:
  system.[]=(s: var seq[T], x: Slice[int], b: openarray[T])
  system.[]=(s: var string, x: Slice[int], b: string)
  system.[]=(a: var array[Idx, T], x: Slice[int], b: openarray[T])
  system.[]=(a: var array[Idx, T], x: Slice[Idx], b: openarray[T])
  

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• brianrogoff (orginal) [2015-02-23T22:14:20+01:00] view original

  Try with the array indexing like

  result.grid[i][j]  =  newCell(i, j)
  Run

  because you have a nested type. You can overload [] to get the other way too if you wish.

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• CharlesH (orginal) [2015-02-23T22:41:28+01:00] view original

  Thanks. That worked fine.

  I do want to index the other way, but I'm going to need to be more comfortable with nim before I try it.

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