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89 version_array2d

%--------------------------------------------------%
% Copyright (C) 2004-2006, 2011 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.
% vim: ft=mercury ts=4 sw=4 et wm=0 tw=0
%--------------------------------------------------%
% 
% File: version_array2d.m.
% Author: Ralph Becket <rafe@cs.mu.oz.au>.
% Stability: medium-low.
% 
% Two-dimensional rectangular (i.e. not ragged) version arrays.
% 
% See the header comments in version_array.m for more details about version
% structures.
% 
%--------------------------------------------------%
%--------------------------------------------------%

:- module version_array2d.
:- interface.

:- import_module list.

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

    % A version_array2d is a two-dimensional version 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 version_array2d(T).

    % version_array2d([[X11, ..., X1N], ..., [XM1, ..., XMN]]) constructs a 2d
    % version array of size M * N, with the special case that
    % bounds(version_array2d([]), 0, 0).
    %
    % An exception is thrown if the sublists are not all the same length.
    %
:- func version_array2d(list(list(T))) = version_array2d(T).
    
    % init(M, N, X) = version_array2d([[X11, ..., X1N], ..., [XM1, ..., XMN]])
    % where each XIJ = X.
    %
    % An exception is thrown if M < 0 or N < 0.
    %
:- func init(int, int, T) = version_array2d(T).

    % version_array2d([[X11, ..., X1N], ..., [XM1, ..., XMN]]) ^ elem(I, J) = X
    % where X is the J+1th element of the I+1th row (i.e. indices start from
    % zero.)
    %
    % An exception is thrown unless 0 =< I < M, 0 =< J < N.
    %
:- func version_array2d(T) ^ elem(int, int) = T.

    % ( VA2D0 ^ elem(I, J) := X ) = VA2D
    % where VA2D ^ elem(II, JJ) = X                    if I = II, J = JJ
    % and   VA2D ^ elem(II, JJ) = VA2D0 ^ elem(II, JJ) otherwise.
    %
    % An exception is thrown unless 0 =< I < M, 0 =< J < N.
    %
    % A predicate version is also provided.
    %
:- func ( version_array2d(T) ^ elem(int, int) := T  ) = version_array2d(T).
:- pred set(int::in, int::in, T::in, version_array2d(T)::in,
            version_array2d(T)::out) is det.

    % bounds(version_array2d([[X11, ..., X1N], ..., [XM1, ..., XMN]), M, N)
    %
:- pred bounds(version_array2d(T)::in, int::out, int::out) is det.

    % in_bounds(version_array2d([[X11, ..., X1N], ..., [XM1, ..., XMN]), I, J)
    % succeeds iff 0 =< I < M, 0 =< J < N.
    %
:- pred in_bounds(version_array2d(T)::in, int::in, int::in) is semidet.

    % lists(version_array2d([[X11, ..., X1N], ..., [XM1, ..., XMN])) =
    %     [[X11, ..., X1N], ..., [XM1, ..., XMN]]
    %
:- func lists(version_array2d(T)) = list(list(T)).

    % copy(VA2D) returns a copy of VA2D with O(1) access times.
    %
:- func copy(version_array2d(T)) = version_array2d(T).

    % resize(VA2D, M, N, X) returns a copy of VA2D resized to M * N.
    % Items with coordinates in common are copied from VA2D; other
    % items are initialised to X.
    %
    % An exception is thrown if M < 0 or N < 0.
    %
:- func resize(version_array2d(T), int, int, T) = version_array2d(T).

    % unsafe_rewind(VA2D) returns a new 2d version array with O(1) access
    % times, at the cost of rendering VA2D and its descendants undefined.
    % Only call this function if you are absolutely certain there are no
    % remaining live references to VA2D or any descendent of VA2D.
    %
:- func unsafe_rewind(version_array2d(T)) = version_array2d(T).

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


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