[Rcpp-devel] Checking for a promise

[Dirk Eddelbuettel]

On 26 December 2010 at 13:36, Gabor Grothendieck wrote:
| On Sun, Dec 26, 2010 at 12:07 PM, Dirk Eddelbuettel <edd at debian.org> wrote:
| >
| > On 25 December 2010 at 17:22, Gabor Grothendieck wrote:
| > | It seems that there are no facilities for this in Rcpp -- at least I
| > | haven't found them.  It seems one has to go one level lower to do
| >
| > Patches are always welcome, particularly if they come with use cases
| > motivating them ("Does it make things easier? Or faster? Or at least make
| > them possible?")  as well as unit tests and documentation.
| >
| > | this.  The code below works.  It passes an environment and name and
| > | returns the type code.  I think this sort of functionality was
| > | intentionally left out of R itself and if one were just trying to
| > | emulate R then I can understand it not being there but since Rcpp is
| > | intended for performance it might be a good idea to give this sort of
| > | access to promises without forcing the program to use the lower level
| > | facilities.
| >
| > Well, why?  I do not use delayedAssign() all that much in R; I haven't needed
| 
| I did address this already in the paragraph you quote but in case it
| wasn't clear its to make the code run faster.  Promises that are not
| used never need be evaluated saving the time that such evaluation
| would have otherwise taken.

Why would I pass an expression I never expect to be evaluated?

Dirk

-- 
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com