Extends a object
via a mechanism known as "parasitic inheritance".
Simply speaking this method "extends" the class of an object. What is actually
happening is that it creates an instance of class name ...className,
by taking another object and add ...className to the class
list and also add all the named values in ... as attributes.
The method should be used by the constructor of a class and nowhere else.
## Default S3 method: extend(this, ...className, ...)
this |
Object to be extended. |
...className |
The name of new class. |
... |
Attribute fields of the new class. |
Returns an object of class ...className.
Henrik Bengtsson
setConstructorS3("MyDouble", function(value=0, ...) {
extend(as.double(value), "MyDouble", ...)
})
setMethodS3("as.character", "MyDouble", function(object, ...) {
fmtstr <- attr(object, "fmtstr")
if (is.null(fmtstr))
fmtstr <- "%.6f"
sprintf(fmtstr, object)
})
setMethodS3("print", "MyDouble", function(object, ...) {
print(as.character(object), ...)
})
x <- MyDouble(3.1415926)
print(x)
x <- MyDouble(3.1415926, fmtstr="%3.2f")
print(x)
attr(x, "fmtstr") <- "%e"
print(x)
setConstructorS3("MyList", function(value=0, ...) {
extend(list(value=value, ...), "MyList")
})
setMethodS3("as.character", "MyList", function(object, ...) {
fmtstr <- object$fmtstr
if (is.null(fmtstr))
fmtstr <- "%.6f"
sprintf(fmtstr, object$value)
})
setMethodS3("print", "MyList", function(object, ...) {
print(as.character(object), ...)
})
x <- MyList(3.1415926)
print(x)
x <- MyList(3.1415926, fmtstr="%3.2f")
print(x)
x$fmtstr <- "%e"
print(x)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.