the man page for relational operators (see, e.g., ?'<') says:
"
Binary operators which allow the comparison of values in atomic vectors.
Arguments:
x, y: atomic vectors, symbols, calls, or other objects for which
methods have been written.
"
it is somewhat surprizing that the following works:
'<'(1)
# logical(0)
'<'()
# logical(0)
'<'(1,2,3)
# TRUE
what does 'binary' mean here, precisely? in the first two examples, one
might suspect that '<' treats the missing arguments as missing values,
but this would not be coherent with what the man page says:
"
Missing values ('NA') and 'NaN' values are regarded as
non-comparable even to themselves, so comparisons involving them
will always result in 'NA'.
"
i can't find the above explained in the documentation. typing `<` shows
that it is a
function(e1, e2) .Primitive("<")
how come can/should it work with no complaint on input that does not
consist of exactly 2 arguments?
in scheme (which is claimed to have been an inspiration for r), < works
on an arbitrary number of arguments:
(<)
;; #t
(< 1)
;; #t
(< 1 2 3)
;; #t
(< 1 2 0)
;; #f
but there < is an arity-dispatched procedure, not a binary one, and it
produces sensible output for any number of arguments (arguably for n=0, 1).
vQ
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