R crashes when printing a named numeric vector of a specific class - Bug?

Le mardi 11 septembre 2012 ? 16:53 +0200, Basil Abou El-Komboz a ?crit :

Dear useR's,

today I stumbled over an interesting phenomenon: First, I created a
named numeric vector with a certain class and several attributes via the
structure() function. After that, I implemented a simple print method
for this class. When calling this function it produces an endless loop
of print calls until R crashes. :/

What is going on here? Is this a bug or have I done something completely
wrong? :)

Below is a minimal example which reproduces the behavior. Be careful
when calling foo() as this automatically calls print.bar() which causes
R to crash (at least on my PC, see further informations about my system below.)

Greetings,
Basil

--------------------------------------------------

Minimal example:

foo <- function () {
 x <- c("A" = 1.3, "B" = 0.7, "C" = -0.3)
 structure(x, class = "bar")
}

print.bar <- function (x, ...) {
  print(x, ...)
}

What is your code supposed to do exactly? ;-)

You're calling print() in your class' print.bar() function, so calling
print() on such an object will call print.bar(), which calls print(),
which calls print.bar()... In a few moments the recursion will have gone
so deep that some system limit about the stack size must be reached, and
R is killed.

If you just want to print the object as a vector, you do not need to
define any function. Or, at least, call print.default() instead of the
generic print().


My two cents