what's preventing additions to the current set of R reserved words/symbols?

Question

Is there a historical precedent of internal changes to the R parser, adding new reserved words or symbols?

If I remember correctly data.table uses a serendipitous := that was once defined but left unused in R internals, but I'm not aware of others. However, as the language evolves, it would sometimes seem useful to define new symbols.

An obvious case could be made for magrittr's pipe %>% which has become ubiquitous for many, but remains a pain to type (sure, there are keyboard tricks, but still). Similarly, dplyr/rlang introduce/repurpose notations for "tidy evaluation" (!!, !!!, :=, ~, etc.).

Another case I'm seeing is the verbosity of lambda functions. Would it be possible, theoretically, to define internally something like f = λ(x) x+1 instead of f = function(x) x+1, or are there character restrictions on top of other reasons?

Answer 1

Why add an ergonomics feature if you risk breaking a runtime that hosts a huge ecosystem? Also, once you add one feature, you are on a slippery slope and are staring straight in the face of feature bloat.

And if you say that we can be smart and judicious about what features we add, how do we structure that decision process? R does not have a "benevolent dictator" having a final word in decisions like this so you are left with design by committee with all that it entails.

The big thing with R has always been the package ecosystem, in which if you want a feature you write it yourself -- as in your magrittr example. The language itself has remained close to its S roots and has successfully served as a stable platform for all the development that has been happening.