examples/manual/slice_array.cpp

/**************************************************************************
 *
 * slice_array.cpp -- Valarray slice array examples
 *
 * $Id: //stdlib/dev/examples/stdlib/manual/slice_array.cpp#12 $
 *
 ***************************************************************************
 *
 * Copyright (c) 1994-2005 Quovadx,  Inc., acting through its  Rogue Wave
 * Software division. Licensed under the Apache License, Version 2.0 (the
 * "License");  you may  not use this file except  in compliance with the
 * License.    You    may   obtain   a   copy   of    the   License    at
 * http://www.apache.org/licenses/LICENSE-2.0.    Unless   required    by
 * applicable law  or agreed to  in writing,  software  distributed under
 * the License is distributed on an "AS IS" BASIS,  WITHOUT WARRANTIES OR
 * CONDITIONS OF  ANY KIND, either  express or implied.  See  the License
 * for the specific language governing permissions  and limitations under
 * the License.
 * 
 **************************************************************************/

#include <iostream>    // for cout, endl
#include <valarray.h>  // Includes valarray and provides stream inserter.
#include <examples.h>  // Generic header for all examples.

typedef std::valarray<int> valarray_t;

int main(void) {

    valarray_t::value_type ibuf[9] = {0,1,2,3,4,5,6,7,8};

    // Create a valarray initialized to the sequence of integers above.
    valarray_t vi (ibuf,9);

    std::cout << "original valarray vi\n\n" << vi << "\n\n";

    // Display a slice of the valarray.
    std::cout << "vi[slice(0,3,3)]\n\n"  << vi[std::slice(0,3,3)] << "\n\n";

    // Unfortunately, slice_arrays were not designed to be easily combined.
    // An explicit conversion to valarray is required, leaving us with
    // this awkward casting syntax.
    vi[std::slice (0,3,3)] = static_cast<valarray_t>(vi[std::slice (1,3,3)]) +
                             static_cast<valarray_t>(vi[std::slice (2,3,3)]);

    // The operation above uses slices ([0-2],3,3) to treat our valarray
    // as a 3-dimensional array:
    //
    //  0 1 2                 3 = 1 + 2
    //  3 4 5                 9 = 4 + 5
    //  6 7 8                15 = 7 + 8
    //  | | |                 |   |   |
    //  | | --slice(2,3,3)    |   |   -slice_array for arithmetic operand.
    //  | ----slice(1,3,3)    |   -----slice_array for arithmetic operand.
    //  ------slice(0,3,3)    ----slice_array assignment refers to valarray.

    std::cout << "vi[slice(0,3,3)] = vi[slice(1,3,3)] + vi[slice(2,3,3)]\n\n"
              << vi << std::endl;

    return 0;
}