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2 array2d

%--------------------------------------------------%
% vim: ft=mercury ts=4 sw=4 et wm=0 tw=0
%--------------------------------------------------%
% Copyright (C) 2003, 2005-2007, 2011-2012 The University of Melbourne.
% This file may only be copied under the terms of the GNU Library General
% Public License - see the file COPYING.LIB in the Mercury distribution.
%--------------------------------------------------%
% 
% File: array2d.m.
% Author: Ralph Becket <rafe@cs.mu.oz.au>.
% Stability: medium-low.
% 
% Two-dimensional rectangular (i.e. not ragged) array ADT.
%
% XXX The same caveats re: uniqueness of arrays apply to array2ds.
% 
%--------------------------------------------------%
%--------------------------------------------------%

:- module array2d.
:- interface.

:- import_module array.
:- import_module list.

%--------------------------------------------------%

    % A array2d is a two-dimensional array stored in row-major order
    % (that is, the elements of the first row in left-to-right
    % order, followed by the elements of the second row and so forth.)
    %
:- type array2d(T).

:- inst array2d ---> array2d(ground, ground, array).

    % XXX These are work-arounds until we get nested uniqueness working.
    %
:- mode array2d_di == di(array2d).
:- mode array2d_ui == in(array2d).
:- mode array2d_uo == out(array2d).

    % init(M, N, X) = array2d([[X11, ..., X1N], ..., [XM1, ..., XMN]])
    % where each XIJ = X.  An exception is thrown if M < 0 or N < 0.
    %
:- func init(int, int, T) = array2d(T).
:- mode init(in, in, in) = array2d_uo is det.
    
    % array2d([[X11, ..., X1N], ..., [XM1, ..., XMN]]) constructs a array2d
    % of size M * N, with the special case that bounds(array2d([]), 0, 0).
    %
    % An exception is thrown if the sublists are not all the same length.
    %
:- func array2d(list(list(T))) = array2d(T).
:- mode array2d(in) = array2d_uo is det.

    % A synonym for the above.
    %
:- func from_lists(list(list(T))) = array2d(T).
:- mode from_lists(in) = array2d_uo is det.

    % array2d([[X11, ..., X1N], ..., [XM1, ..., XMN]]) ^ elem(I, J) = X
    % where X is the J+1th element of the I+1th row (that is, indices
    % start from zero.)
    %
    % An exception is thrown unless 0 =< I < M, 0 =< J < N.
    %
:- func array2d(T) ^ elem(int, int) = T.
%:- mode array2d_ui ^ elem(in,  in ) = out is det.
:- mode in       ^ elem(in,  in ) = out is det.

    % T ^ unsafe_elem(I, J) is the same as T ^ elem(I, J) except that
    % behaviour is undefined if not in_bounds(T, I, J).
    %
:- func array2d(T) ^ unsafe_elem(int, int) = T.
%:- mode array2d_ui ^ unsafe_elem(in,  in ) = out is det.
:- mode in       ^ unsafe_elem(in,  in ) = out is det.

    % ( T0 ^ elem(I, J) := X ) = T
    % where T ^ elem(II, JJ) = X                 if I = II, J = JJ
    % and   T ^ elem(II, JJ) = T0 ^ elem(II, JJ) otherwise.
    %
    % An exception is thrown unless 0 =< I < M, 0 =< J < N.
    %
:- func ( array2d(T) ^ elem(int, int) := T  ) = array2d(T).
:- mode ( array2d_di ^ elem(in,  in)  := in ) = array2d_uo is det.

    % Pred version of the above.
    %
:- pred set(int, int, T,  array2d(T), array2d(T)).
:- mode set(in,  in,  in, array2d_di, array2d_uo) is det.

    % T ^ unsafe_elem(I, J) := X is the same as T ^ elem(I, J) := X except
    % that behaviour is undefined if not in_bounds(T, I, J).
    %
:- func ( array2d(T) ^ unsafe_elem(int, int) := T  ) = array2d(T).
:- mode ( array2d_di ^ unsafe_elem(in,  in)  := in ) = array2d_uo is det.

    % Pred version of the above.
    %
:- pred unsafe_set(int, int, T,  array2d(T), array2d(T)).
:- mode unsafe_set(in,  in,  in, array2d_di, array2d_uo) is det.

    % bounds(array2d([[X11, ..., X1N], ..., [XM1, ..., XMN]), M, N)
    %
:- pred bounds(array2d(T), int, int).
%:- mode bounds(array2d_ui, out, out) is det.
:- mode bounds(in,       out, out) is det.

    % in_bounds(array2d([[X11, ..., X1N], ..., [XM1, ..., XMN]), I, J)
    % succeeds iff 0 =< I < M, 0 =< J < N.
    %
:- pred in_bounds(array2d(T), int, int).
%:- mode in_bounds(array2d_ui, in,  in ) is semidet.
:- mode in_bounds(in,       in,  in ) is semidet.

    % lists(array2d([[X11, ..., X1N], ..., [XM1, ..., XMN])) =
    %     [[X11, ..., X1N], ..., [XM1, ..., XMN]]
    %
:- func lists(array2d(T)) = list(list(T)).
%:- mode lists(array2d_ui) = out is det.
:- mode lists(in        ) = out is det.

%--------------------------------------------------%
%--------------------------------------------------%


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