On 06/05/2014 2:09 PM, Göran Broström wrote:
A thread on r-devel ("Historical NA question") went (finally) off-topic,
heading towards "Precedence". This triggered a question that I think is
better put on this list:
I have been more or less regularly been writing programs since the
seventies (Fortran, later C) and I early got the habit of using
parentheses almost everywhere, for two reasons. The first is the
obvious, to avoid mistakes with precedences, but the second is almost as
important: Readability.
Now, I think I have seen somewhere that unnecessary parentheses in R
functions may slow down execution time considerably. Is this really
true, ant should I consequently get rid of my faiblesse for parentheses?
Or are there rules for when it matters and doesn't matter?
I think "considerably" is an exaggeration, but they are kept as part of
the expression, and they do take a little bit of execution time.
The reason is to support the difference between
(x <- 1)
and
x <- 1
but they are kept even when they make no difference (other than to slow
things down).
Duncan Murdoch
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