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To: Pierre Weis <pierre.weis@inria.fr>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] Python's yield, Lisp's call-cc or C's setjmp/longjmp in OCaml
References: <200312171914.UAA00389@pauillac.inria.fr>
From: Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>
Date: 17 Dec 2003 20:32:17 +0100
In-Reply-To: <200312171914.UAA00389@pauillac.inria.fr>
Message-ID: <87r7z31br2.fsf@student.uni-tuebingen.de>
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Pierre Weis <pierre.weis@inria.fr> writes:

> [...]
> > This only works for simple examples. Try for example writing a
> > function which successively yields all possible moves for a chess
> > board. The "yield" operator really helps there.
> 
> Very interesting: please give us the code corresponding to this
> example, in order for us to realize how the full power of the "yield"
> operator helps to solve this problem.

I don't really know Python well (nor chess)... it would probably look
similar to:

def moves(board):
  for x in range(0, 8):
    for y in range(0, 8):
      if board.at(x, y) == PAWN:
        yield Move(x, y, x + 1)
      elif board.at(x, y) == ROOK:
        for dx, dy in [(-1, 0), (1, 0), (0, -1), (0, 1)]:
          n = 0
          while is_on_board(x + n*dx, y + n*dy):
            yield Move(x, y, x + n*dx, y + n*dy)
            n += 1
      ...

-- 
	Falk

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