rand VS json

Making compatibility promises for distributions means they cannot take advantage of potential advancements in the field.

Defining an error type that is meaningful, portable, and compatible with no-std isn't straightforward. If the std lib's getrandom requires std, then just like that, rand and many other crates won't use it anyway. Using io::Result seems to me to face this challenge.

Some wasm targets can’t generate random numbers at all but in the case of the book because you are using wasm in a browser you can use JS to generate random numbers. I believe there’s a way to get the rand crate to use JS as the backend for generating rand but its a bit more convoluted than the easy one-liner that the book suggests.

rand

This uses rand and xcomplex to handle the mathematics, png to write image files, and dialoguer and indicatif for some pretty prompts and progress bars.

You can often achieve this without any unsafe by putting an assert!() on the length before the hot loop. For example, I got rid of some unsafe in rand that way.

This is a widely used method to map random integers to floating point numbers, but it has the disadvantage of wasting 1 bit of float mantissa precision.

On modern CPUs, its computational advantage over full-precision mapping methods, such as multiplication by a float, is not always clear [1].

[1] https://github.com/rust-random/rand/issues/416

In fact, there are a lot of crates in Rust where in other programming languages, it would be included in the standard library. Examples are regex, random number generators, additional iterator methods, macros for other collections, num traits, loggers, HTTP libraries, error handling, async runtimes, serialization and deserialization, date and time, and many more.

Oh wow. So serde_json doesn't roundtrip floats by default, it uses some imprecise faster algorithm https://github.com/serde-rs/json/issues/707

Good thing there's msgpack I guess.

tokio / hyper / toml / serde / serde_json / json5 / console

Serde JSON, an extension of the serde crate that enables the serialization and deserialization of Rust structs.

To serialize and deserialize data, we'll employ the popular serde crate along with serde_json. This will allow us to easily convert between Rust types and JSON when working with API requests and responses. For async operations we'll use the Rust futures crate.

From the Cargo.toml file above, we can see that the Perseus version at the time of publication is 0.4.2 and has the following dependencies that are common to both the engine side (server-side) and client side of a Perseus application: sycamore, serde, and serde_json.

serde_json

Number parsing uses a fairly naive but uses a lossless algorithm in musli-json. In serde_json they use a fork of lexical I haven't wrapped my head around. I wanted something simple to start with.

Your best best would be to use an enum. Either your own or something like the one from serde_json depending on what you are trying to do.

Don't do that if you care about memory usage. In your toy program, I wouldn't be surprised if memory usage was a lot better if you used Box instead. (even if it doesn't look like it, you can handle almost all the use cases of serde_json::Value with it, often not much less convenient)