[R] assert( condition )

[ivo welch]

hi R wizards:  I think it would be a good idea for me to use basic 
argument checking (type, length) in function calls via an assert() like 
function.  How do people usually do this?  Should I define my own 
"assert()" function (or are there some predefined assertions)?  If I 
write my own assert, is it possible to print out the R internal call 
stack?  thanks.

(?assert and google "assert R" and V+D index do not point me the right way.)

regards, /iaw