If I define this function R> ask <- function (message = "Type in datum") eval(parse(prompt = paste(message, ": ", sep = ""))) the following is produced as expected on a Linux/debian machine R> ask("input") input: 3 [1] 3 R> ask("input") input: 3:6 [1] 3 4 5 6 R> ask("input") input: c(3,6) [1] 3 6 If I run exactly the same on a Mac (OS X 10.5.6), it still works provided R is run in a Terminal window. The outcome changes if R is run in "its own window", started by clicking on its icon; the first two examples are still Ok, the third one produces: *** caught segfault *** address 0x4628c854, cause 'memory not mapped' R> sessionInfo() # before crash! R version 2.8.1 (2008-12-22) i386-apple-darwin8.11.1 locale: en_GB.UTF-8/en_GB.UTF-8/C/C/en_GB.UTF-8/en_GB.UTF-8 attached base packages: [1] stats utils datasets grDevices graphics methods base R> R.version _ platform i386-apple-darwin8.11.1 arch i386 os darwin8.11.1 system i386, darwin8.11.1 status major 2 minor 8.1 year 2008 month 12 day 22 svn rev 47281 language R version.string R version 2.8.1 (2008-12-22) -- Adelchi Azzalini <azzalini at stat.unipd.it> Dipart.Scienze Statistiche, Universit? di Padova, Italia tel. +39 049 8274147, http://azzalini.stat.unipd.it/