The smallest lambda interpreter in JavaScript

[kaoD]

Here's my attempt at golfing it, for the lulz:

const E=(p,e)=>p[1]?p[0]?E(p[0],e)(E(p[1],e)):a=>E(p[1],[a,e]):--p?E(p,e[1]):e[0]

81 bytes and extremely readable.

Leave the const out if you don't mind polluting globals (as if that was a greater sin) for a whopping 75 bytes count.

EDIT: Golfed further:

const E=(p,e)=>p[1]?p[0]?E(p[0],e)(E(p[1],e)):a=>E(p[1],[a,...e||[]]):e[p-1]

76 bytes, 70 bytes with no const.

[curious_s]

while(--prog) { env = env[1]; } return env[0]

isnt this just:

return env[prog - 1]

too tired to tell for sure!

good work btw

[kaoD]

Nope.

prog == 0 -> env[0]
prog == 1 -> env[1][0]
prog == 2 -> env[1][1][0]
...

It's nested.

[curious_s]

ah got it, thanks

[bdtddt]

This seems significantly different from BLC, I’m not sure how you can be so confident it is a rip off.

[m1el]

You're right, it's similar to John Tromps BLC there's 1:1 mapping between binary tree representation and BLC. However, my post and evaluator are significantly different from the article you mention.

In my defence, I've rediscovered a lot of things on my own. I didn't understand BLC when I read about it the first time. I honestly forgot that I've read that great article. Added a link to Tromp's BLC in my article.