i believe the following is true but would appreciate confirmation
that it is intended behavior and will continue:
if a default argument is employed in the definition of a generic
function, and the generic is called with the argument in question
(call it 'ARG') missing, then the method for signature (..., ARG =
"missing", ...) will be called by 'standardGeneric' whether or not
ARG is evaluated in the body of the generic prior to the call to
'standardGeneric'; however, the value assigned to ARG in the method
call will depend on whether ARG was evaluated in the body of the
generic prior to the call to 'standardGeneric' (with the default
value assigned in the case of prior evaluation and no value assigned
in the case of no prior evaluation). furthermore, if ARG is
explicitly assigned to in the body of the generic prior to the call
to 'standardGeneric', then the method for signature (..., ARG = class
(ARG), ...) will be called, with the assigned value of ARG passed to
the call.
this behavior is exhibited by the code below:
__
setGeneric("foo", function(x = 1) standardGeneric("foo"),
useAsDefault = FALSE)
setMethod("foo", signature(x = "missing"), function(x = 3) x)
setGeneric("foo2", function(x = 1) {x; standardGeneric("foo2")},
useAsDefault = FALSE)
setMethod("foo2", signature(x = "missing"), function(x = 3) x)
setGeneric("foo3", function(x = 1) {x<-2; standardGeneric("foo3")},
useAsDefault = FALSE)
setMethod("foo3", signature(x = "missing"), function(x = 3) x)
setMethod("foo3", signature(x = "numeric"), function(x = 3) x^2)
foo() # returns 3
foo2() # returns 1
foo3() # returns 4
___
franklin parlamis
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