/*
 *  call-seq:
 *     clause.occur = occur -> occur
 *
 *  Set the +occur+ value for this BooleanClause. +occur+ must be one of
 *  +:must+, +:should+ or +:must_not+.
 */
static VALUE
frt_bc_set_occur(VALUE self, VALUE roccur)
{
    GET_BC();
    enum BC_TYPE occur = frt_get_occur(roccur);
    bc_set_occur(bc, occur);

    return roccur;
}