[Zope-dev] an Interface expressing "a list of generator function"

[Tres Seaver]

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On 11/08/2010 04:40 AM, Jean-Daniel wrote:
> Hello,
> 
> I have two objects which interoperate to solve a sudoku: the Sudoku class
> and a vector (a list actually) of generator functions. The Sudoku interface
> is simple to write as it requires three functions and an attribute.
> 
> class ISudoku:
> 
>     board = Attribute()
> 
>     def free(col, line):
>         "frees the slot at position col, line"
> 
>     def set(col, line, value):
>         "Sets the value in the slot at position col, line"
> 
>     def candidates(col, line):
>         "Returns the candidate digits for the slot at position col,line"
> 
> 
> But how to express "vector of generator functions" with Zope interfaces? I
> want to express the possibility to access the vector object with
> the  [n] index notation, and this returns a function returning a generator
> (an object with an iter and next function).
> 
> Thank you for your help,
> 
> 
> PS: the vector of generator functions is the input of the algorithm called
> "conjoin", used to solve the eight queen problem and knight's tour problem.
> It is described in the Python sources
> (Python-2.6.5/Lib/test/test_generators.py).
> 
> PPS: I say vector instead of list even when the vector is a list, because
> "list" usually  implies the possibility to append elements dynamically which
> is not pertinent in this problem. The length of the vector won't change and
> is equal to the number of slots on a sudoku board.


I would specify the contracts omething like so::


class IVector(Interface):

    item_type = Attribute(u"Interface of items.")

    def __len__():
        """ Fixed length of vector.
        """

    def __getitem__(index):
        """ Return the 'index'th item.

        Items conform to 'item_type'.

        'index' must be an integer between 0 and __len__() - 1,
        else raise IndexError.
        """

class IIterable(Interface):

    def __iter__():
        """ Return an iterator for this object.
        """




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Tres Seaver          +1 540-429-0999          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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