[Rd] Inconsistencies in sum() (PR#1408)

[ripley@stats.ox.ac.uk]

R 1.4.1

sum() tries to keep the result integer, although that is not
currently documented (and I am about to change it).

> x <- as.integer(2^30)
> x

1) inconsistent in warning or not:

> sum(x, x)
[1] NA
> sum(c(x, x))
[1] NA
Warning message:
Integer overflow in sum(.); use sum(as.numeric(.))

2) It's order-dependent:

> sum(0.0, x, x)
[1] 2147483648
> typeof(.Last.value)
[1] "double"
> sum(x, x, 0.0)
[1] NA
> typeof(.Last.value)
[1] "double"

I believe that it should calculate in integers only if *all* the
arguments are integers, that is behave like

> sum(c(x, x, 0.0))
[1] 2147483648


-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595


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