gstat.set <- function(set) {
	if(!is.list(set))
		stop("set should be a list")
	if (length(set) == 0)
		return(NULL)
	ret = NULL
	n = names(set)
	for (i in (1:length(set))) {
		val = set[[i]]
		if (is.character(val))
			val = paste("'", val, "'", sep = "")
		str = paste("set ", n[i], " = ", val, ";", sep="")
		ret = c(ret, str)
	}
	ret
}

gstat.load.set <- function(set) {
	str = gstat.set(set)
	if (!is.null(str)) {
		ret = .Call("gstat_load_command", str)
		if (ret != 0)
			stop(paste("error occured when parsing command:", str[ret]))
	}
	invisible()
}

gstat.load.merge <- function(obj) {
	gstat.merge <- function(obj) {
		ret = NULL
		for (i in 1:length(obj$merge)) {
			m = obj$merge[[i]]
			if (is.character(m) && length(m) == 4) {
				id = match(m[c(1,3)], names(obj$data)) - 1 # name ->> id
				if (any(is.na(id)))
					stop(paste("could not match all ids:", m[c(1,3)]))
				col = as.integer(m[c(2,4)]) - 1
				if (any(is.na(col)) || any(col < 0))
					stop("merge: parameters should be positive integers")
				str = paste("merge", id[1], "(", col[1], ") with", id[2], 
						"(", col[2], ");")
				ret = c(ret, str)
			} else stop(
				"list elements of merge should be lenght 4 character vectors")
		}
		ret
	}

	if (is.character(obj$merge) && length(obj$merge) == 2)
		obj$merge = list(c(obj$merge[1], 1, obj$merge[2], 1))
	if (is.list(obj$merge)) {
		str = gstat.merge(obj)
		ret = .Call("gstat_load_command", str)
		if (ret != 0)
			stop(paste("error occured when parsing command:", str[ret]))
	} else 
		stop("merge argument should be list or character vector of lenght 2")
}