# fields  is a package for analysis of spatial data written for
# the R software environment .
# Copyright (C) 2018
# University Corporation for Atmospheric Research (UCAR)
# Contact: Douglas Nychka, nychka@ucar.edu,
# National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307-3000
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with the R software environment if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
# or see http://www.r-project.org/Licenses/GPL-2    
test.for.zero <- function(xtest, xtrue, tol = 1e-08, 
    relative = TRUE, tag = NULL) {
    denom <- ifelse(relative, mean(abs(c(xtrue))), 1)
    test.value <- sum(abs(c(xtest) - c(xtrue)))/denom
    if (!is.null(tag)) {
      cat("Testing: ", tag, fill = TRUE)
    }
    if (test.value < tol) {
            cat("PASSED test at tolerance ", tol, fill = TRUE)
    }
    else {

          cat("FAILED test value = ", test.value, " at tolerance ", 
            tol)
# generate an "error" to signal failed test      
      if (exists("test.for.zero.flag")) {
        stop()
      }
    }
}