if (!(a instanceof ExprString))
return ExprError.VALUE;
String s = ((ExprString) a).str;
if ("directory".equalsIgnoreCase(s)) {
return new ExprString(System.getProperty("user.dir"));
} else if ("memavail".equalsIgnoreCase(s)) {
return new ExprDouble(Runtime.getRuntime().freeMemory());
} else if ("memused".equalsIgnoreCase(s)) {
return new ExprDouble(Runtime.getRuntime().totalMemory() -
Runtime.getRuntime().freeMemory());