im-rs VS im-lists

They're using hash array mapped tries. I don't have my own personal implementation, I have been using https://github.com/bodil/im-rs until I can get around to making my own implementation (not that I really need to, but it would be a fun exercise).

Functions generate a hash based on a unique id generated for the function, plus the hash of any captured variables, and a hash of the pointer address to the function). That is off the top of my head though so I could be missing some details.

Hashing maps is tricky! With a sufficiently deep hash map you can run into problems since that invokes an equality check as well - at least how I handle it, is that you just attempt to naively hash the keys and values of the hash map, to create a hash code for that object. If the equality check ends up with a sufficiently large depth, eq returns false so we don't stack overflow.

Too late my friend ;) https://github.com/bodil/im-rs

There’s also im.

rc/Cargo.toml specifies paths such as ../src/lib.rs and ../build.rs to point at the same source files

If you indeed do care about access to historical versions of data, take a look at the I’m crate: https://github.com/bodil/im-rs

To answer each of these:

1. I do support parameters now, syntax parameters not yet. I would like to! But Racket has a pretty hefty head start on me so it'll take some time.

2. Right now I have syntax-rules macros, I also have defmacro style macros that get used internally in the kernel during expansion, but haven't yet opened them up for user space yet. Syntax case will be coming soon hopefully.

3. The odds of me being able to come up with an implementation to match typed racket pound for pound is pretty low. I have toyed with using contracts as types (where possible), with medium/promising success in certain situations. I have a soft spot for racket and have been modeling behavior after it, however it will take time to be able to create a macro system powerful enough to match it. It wouldn't be impossible to create an alternative syntax to just lower to steel after type checking, but I haven't put time into that.

On the list type - the list in use currently is an unrolled linked list https://github.com/mattwparas/im-lists, which I've found to yield much better performance for iteration than the naive linked lists. When possible, the vm does some in place mutation on the lists as well when consing, which helps performance as well. I also can hot swap for a vlist, but at the moment have stuck with unrolled linked lists.