fn λ → ÷ = ←

→ and ← can now be used for assignment, not just <- and ->.

function(x) x**3 can now be written fn(x) x**3, λ(x) x**3, or ƒ(x) x**3.

÷ means division.

Existing R spelling remains available: <-, <<-, ->, ->>, ==, and function still work.

answer ← 8 ÷ 2
answer = 4

The last line returns

[1] TRUE

because = now means equal.

this	does
x ← 3	assign
x ↞ 3	assign in an enclosing frame
3 → x	assign
3 ↠ x	assign in an enclosing frame
left = right	test equality
fn(x) expression, λ(x) expression, or ƒ(x) expression	construct a function
left ÷ right	divide

Parameters are still supplied with =.

clean.mean ← λ(x) mean(x, na.rm = TRUE)

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Actually this is worse than I thought it would be, I thought there would be no downsides....

That compatibility is contextual. Inside another call, wrap an equality comparison in parentheses so it cannot be read as an argument name:

stopifnot((answer = 4))

Code that used a single = as assignment must use an arrow in this R. The comma and argument-label rules have otherwise been left alone.

fn also used to be an ordinary name. It is reserved here, so old code using bare fn as a variable or argument must choose another name. This source uses fun; in particular, write optim(par, fun = ...) rather than optim(par, fn = ...).

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You do not have to give up ordinary R

The tested Linux instructions install this build in its own folder and use a separate package library. They do not remove ordinary R, alter your projects, rewrite your scripts, or upload your work. Close this R and launch ordinary R as before whenever you want to switch back.