[broomcorn]

That sounds like asking for trouble. Someone coming from any other programming language could easily forget that expression evaluation is stateful. Better to be explicit and create an object representing a expression. Tell me, at least, that the variable is immutable in that context?

[bnprks]

The good news is that most variables in R are immutable with copy-on-write semantics. Therefore, most of the time everything here will be side-effect-free and any weird editing of the variable bindings is confined to within the function. (The cases that would have side effects are very uncommonly used in my experience)

[nerdponx]

The whole magic is that expressions are in fact just objects in the language. And no, there aren't any immutable bindings here.

[vharuck]

It's crazy how literally R takes "Everything's an object." While parentheses can be treated like syntax when writing code, it's actually a function named `(`.

Of course, playing with magic sounds fun until you remember you're trying to tell a computer to do a specific set of steps. Then magic looks more like a curse.