This is a lambda calculus interpreter, and was something that I did several months back to learn the features of Scala, and something that I still like to play with from time to time. It requires Processing's core library in order to function, since that's what I used to code it's GUI. You can get that from Processing's website
Using it is easy:
Upon starting it up, you'll see a happy colon at the top and several co-centric rings of circles slowly promenading around their shared midpoint. Typing in a number and pressing enter will cause the interface to go through a quick convulsion and yield the number and it's Church numeral printed vertically along the side. Great, huh?
Type this:
> succ := ^n^f^x (n f x)
Then type:
(succ 3)
The output will be:
(4, ^f^x (f (f (f (f x)))))
You see, the > operator will assign a symbol
a meaning to the global environment, so instead
of having to type ^n^f^x (n f x) every time
you want to compute n + 1, you can assign
it a symbol and use that symbol instead.
This example also shows you the rest of the syntax:
^<symbol> <expression> starts a body.
(<expression> <expression> ...) applies some
arguments to an expression.
A <symbol> is any alphabetic string.
All of these count as <expression>s.
This calculator features implicit currying and lexical scope. It has no tail-call optimization. It is call-by-value, so be very weary when using it; the Y-Combinator will end your session very quickly, for example.
I also have no concrete plans for this program, so suggestions and fixes are welcome and very much desired.
The Wikipedia article is a good start as any. It also links to some great resources on the Internet.
If there are problems in using my calculator while following along with the reading, please let me know by posting an issue to this git and I'll do my best to fix the problem.