IMO it should be like Fennel and just support `lambda` and `λ`. The latter is not even that hard to type, in virtually any free (libre) OS you can just

    $ echo '
    <Multi_key> <Y> <Y> : "Λ" # GREEK CAPITAL LETTER LAMDA
    <Multi_key> <y> <y> : "λ" # GREEK CAPITAL LETTER LAMDA
    ' >> ~/.XCompose

If you’re limited by a nonfree OS you should be able to patch the problem with free duct tape like Karabiner or AutoHotKey.

And in vim you can just

    <C-K>*l

in insert mode (which can be done with option-l on macOS if you `inoremap ¬ <C-K>*l` https://apple.stackexchange.com/questions/230422/type-lambda...).

Now imagine doing that same thing for every system you're programming on. And then imagine having to do it for a million different symbols. I'm sure as hell glad you're not in charge of any of this.

> Now imagine doing that same thing for every system you're programming on.

As a matter of fact, I already do, the XCompose way.

  yadm clone /path/to/dotfiles/repo.git¹

As for the vim way, why would I use a system without vim²?

> And then imagine having to do it for a million different symbols.

I don’t know other symbols as useful as this, but sure, either of my solutions scales fine (`yadm clone` shouldn’t get bogged down by any repo smaller than the Linux kernel’s). My system's /usr/share/X11/locale/en_US.UTF-8/Compose already has a section for APL’s symbols out of the box.

¹yadm is dumb by the way, any symlink manager + git/hg is probably better

²As it so happens, I do: because vim is bloat and https://sr.ht/~martanne/vis/ fits much better in the ramdisk my OS always runs in — but I’d bet 99.99% ±0.009% of programmers install their OS on an HDD/SSD and don’t care.

A better solution is just to use the word 'lambda', and let your text editor render it as a lambda symbol if you want (my emacs does this).

How is it different than the word "function"?

It's not, that's why people use arrow syntax in languages like Javascript for short in-lined functions.

In Windows, WinCompose lets you set up compose keys like that, although the default ⋄yy goes to ʎ.

I don’t think R yet has native Unicode support on every platform.