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Is there "orphan code" in seq.default?

2 messages · David Winsemius, Martin Morgan

David Winsemius
# 
I was looking at the code in seq.default and saw code that I think would throw an error if it were ever executed, although it will not because there is first a test to see if one of its arguments is missing. Near the end of the function body is this code:

    else if (missing(by)) {
        if (missing(to)) 
            to <- from + length.out - 1L
        if (missing(from)) 
            from <- to - length.out + 1L
        if (length.out > 2L) 
            if (from == to) 
                rep.int(from, length.out)
            else as.vector(c(from, from + seq_len(length.out - 
                2L) * by, to))

Notice that the last call to `else` would be returning a value calculated with 'by' which was already established as missing.
Martin Morgan
#
On 08/15/2015 02:01 PM, David Winsemius wrote:
missing arguments can have default values

 > f = function(by="sea") if (missing(by)) by
 > f()
[1] "sea"

which is the case for seq.default

 > args(seq.default)
function (from = 1, to = 1, by = ((to - from)/(length.out - 1)),
     length.out = NULL, along.with = NULL, ...)


Martin Morgan