evcxr VS xshell

Emacs didn't invent REPL, and it's common everywhere. For Rust: https://github.com/evcxr/evcxr/blob/main/evcxr_repl/README.m.... But heck, the compiler is reasonably fast enough that any IDE can REPL by compiling the code.

The value here is more in being able to read a script before you run it, then have it run fast, maybe tweaking something here and there. And a compiled script will run 10,000 times faster than LISP, which can be important.

https://github.com/evcxr/evcxr can run Rust in a Jupyter notebook. It's not Golang but close enough.

The engine uses rust_decimal::Decimal to represent high precision decimal numbers, like the weight property. Serialization of RocksDB keys is done by the storekey crate. To know how Yumi's machine stores diffs, we can now ask- How does storekey serialize rust_decimal? Well, using evcxr to run Rust in Jupyter, the answer is as a null-terminated string:

In theory you should be able to create Rust notebooks (Jupyter notebook) using evcxr so maybe some AI, data analysis, prototyping make sense if you aim for good performance in final application (protype in evcxr and use notebook as reference to implement final application in Rust for speed and safety).

You should check out evcxr

There is also implementations of rust REPLs, like the beautifully named evcxr.

Just a few minutes ago I learned about https://github.com/matklad/xshell and it looks nice!

For developer-oriented stuff, there's tools like xshell and cargo-xtask. For operator tasks that need to run in a deployed environment, it's not usually a big lift to add CLI subcommands to your binary. It's certainly more boilerplate and inertia than doing stuff in a live REPL, though, and sometimes difficult to recommend for truly one-off situations.

how was your experience with trying to use [xshell](https://github.com/matklad/xshell/) as a shell script replacement? was the boilerplate worth it?

Also xshell might be helpful here https://github.com/matklad/xshell

* time to compile whatever syn generated

I didn’t do a super thorough studies of things, but my impression is that 2, performance of syn itself, is rarely an issue. Most of the time it is 1) (and the associated problem of decreased build parallelism because half of the crates wait for syn to compile) and 3).

To get a feeling how costly a simple proc macro is, run this benchmark: https://github.com/matklad/xshell/blob/4e5090e9f79baeed1037b....

This is an API vulnerable to shell injection. I think it’s relatively important to design command-running libraries which don’t re-introduce the possibility of this error into Rust. The fix here is to ensure that the string is a compile-time string, and, preferably, even lex it at compile time. See xshell for an example of ergonomic and safe API here: https://github.com/matklad/xshell.

Note that “lexer level” proc macros, which don’t parse rust code, and which don’t generate a ton of Rust code, could be pretty light weight on compile times. Here’s a benchmark one can run to measure that: https://github.com/matklad/xshell/blob/master/tests/it/main.rs#L376