Gabor Csardi writes: > Btw. for some motivation, here is a (surely incomplete) list of > languages with '+' as the string concatenation operator: > > ALGOL 68, BASIC, C++, C#, Cobra, Pascal, Object Pascal, Eiffel, Go, > JavaScript, Java, Python, Turing, Ruby, Windows Powers hell, > Objective-C, F#, Sc-ala, Ya.
The situation for R is rather different from that of a language (as many of the above) in which variables are declared to be of a specific type. In such a statically typed language, when you see the expression "a+b", it is easy to figure out whether the "+" will be numeric addition or string concatenation, by looking at the declarations of "a" and "b". But in a language such as R in which values have types, but variables don't, someone seeing "a+b" in code wouldn't be able to tell easily what it does. This is OK, in fact desirable, in the case of operator dispatch according to class when the different methods implement versions of the operator that have analogous properties. But numeric addition and string concatenation have just about nothing in common, so cases where functions are meant to have "+" be either addition OR concatenation are going to be rare. Furthermore, making "+" concatenate strings would preclude ever making "+" convert strings to numbers (signalling an error if they aren't in some numerical format) and then add them. I'm not sure whether that would be a good idea or not, but it might be unwise to eliminate the possibility. And of course, as someone else mentioned, it may instead be desirable for attempts to add strings to signal an error, as at present, which one also gives up by making "+" do concatenation. > Yes, even Fortran has one, and in C, I can simply write "literal1" > "literal2" and they'll be concatenated. It is only for literals, but > still very useful. Concatenation of literal strings could easily be added to the R parser without changing anything else. (Getting them to deparse as the same two pieces would be tricky, but is maybe not necessary.) Radford Neal ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
