log2(quote(1:10)) evaluates the quoted 1:10, log() does not

On Wed, 10 Mar 2010, William Dunlap wrote:

This is very minor, but shouldn't log2(quote(1:10))
throw an error,the same as log() and other math functions
do?  It looks like log2 and log10 evaluate a call object
instead of throwing a non-numeric-argument error.  They
do object to non-call language objects, like expressions.

Yes, but the reason is complex.  log2 and log10 first look for methods for 
themselves, then for log, and the method dispatch code evaluates the argument 
-- so it gets done twice.  And because of some of the peculiarities of the 
internal S4 dispatch code, it was hard enough to get to work at all.

The simplest solution seems to be to make log2() and log10() special 
primitives (as log is):

the alternative is to duplicate a version of the 
logb() code in log2() and log10().

 > log2(quote(1:10))

  [1] 0.000000 1.000000 1.584963 2.000000 2.321928 2.584963
  [7] 2.807355 3.000000 3.169925 3.321928

 > log(quote(1:10))

 Error in log(quote(1:10)) : Non-numeric argument to mathematical
function

 > sqrt(quote(1:10))

 Error in sqrt(quote(1:10)) :
   Non-numeric argument to mathematical function

 > quote(1:10) ^ 2

 Error in quote(1:10)^2 : non-numeric argument to binary operator

 > 2 ^ quote(1:10)

 Error in 2^quote(1:10) : non-numeric argument to binary operator

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
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