Mike Williamson <this.is....@gmail.com> writes:
> Thanks Sarah, All,
>
> I guess I never thought of a negative sign as an "operation", but
> knowing that it is considered an operation explains everything nicely.
> Somewhere in it's underbelly, I suppose -4 is represented as "0 - 4"?
Not exactly. Here is the list of constituent elements of expressions for -1 and
0 - 1
> as.list(quote(-4))
[[1]]
`-`
[[2]]
[1] 4
> as.list(quote(0-4))
[[1]]
`-`
[[2]]
[1] 0
[[3]]
[1] 4
The first case is unary, the second is binary.
Exercise: See ?Syntax. Write the result of this line:
lapply( as.list( quote(-1-4) ), as.list )
and (thereby) explain why the result of -1-4 isn't 3.
HTH,
Chuck
[rest deleted]
--
Charles C. Berry Dept of Family/Preventive Medicine
cberry at ucsd edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
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