[R] odd feature

[Thomas Lumley]

On Mon, 22 May 2006, Gabor Grothendieck wrote:

> Due to lazy evaluation, I don't think a and b are fully evaluated:
>
>> ifelse(1, a <- 1, b <- 2)
> [1] 1
>> a
> [1] 1
>> b
> Error: object "b" not found

yes. If you look at the code for ifelse() it evaluates the second argument 
if any test values are TRUE and the third argument if any test values are 
FALSE, so in the scalar case it does not evaluate both arguments.

 	-thomas


Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle