array_lbound.c

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/* lbound function */

#include "fb.h"

FBCALL ssize_t fb_ArrayLBound( FBARRAY *array, ssize_t dimension )
{
        /* given dimension is 1-based */
        dimension -= 1;

        /* out-of-bound dimension? */
        if( (dimension < 0) || (dimension >= array->dimensions) ) {
                /*
                 * lbound( a, 0 ) returns the lower bound of the array's dimTB,
                 * always 1. Any other out-of-bound dimension value returns 0.
                 *
                 * Together with ubound returning the dimension count or -1 for
                 * these cases respectively, we can check the dimension count
                 * and detect empty arrays.
                 *
                 * Using lbound=0 and ubound=-1 for empty arrays is good because
                 * it means that lbound > ubound, which is normally invalid,
                 * and lbound staying 0 allows checks such as
                 *    @array(lbound(array)) <> NULL
                 * to keep working.
                 */
                return dimension == -1 ? 1 : 0;
        }

        return array->dimTB[dimension].lbound;
}