Comparison operators == and != can be used on language objects (i.e. call objects and symbols). The == operator in particular often seems to be used as a shorthand for calling identical(). The current implementation involves comparing deparsed calls as strings. This has a number of drawbacks and we would like to transition to a more robust and efficient implementation. As a first step, R-devel will soon be modified to signal an error when the ordered comparison operators <, <=, >, >= are used on language objects. A small number of CRAN and BIOC packages will fail after this change. If you want to check your packages or code before the change is committed you can run the current R-devel with the environment variable setting
_R_COMPARE_LANG_OBJECTS=eqonly where using such a comparison now produces > quote(x + y) > 1 Error in quote(x + y) > 1 : comparison (>) is not possible for language types Best, luke -- Luke Tierney Ralph E. Wareham Professor of Mathematical Sciences University of Iowa Phone: 319-335-3386 Department of Statistics and Fax: 319-335-3017 Actuarial Science 241 Schaeffer Hall email: luke-tier...@uiowa.edu Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel