rsexp

S-expression parsing and writing in Rust using nom parser combinators.

This implemantion aims at being compatible with OCaml's sexplib. The main type for S-expression is as follows:

pub enum Sexp {
    Atom(Vec<u8>),
    List(Vec<Sexp>),
}

Reading and Writing Sexp Files

Reading a sexp file can be done by first reading the whole file content and then converting the resulting slice into a Sexp object as follows:

    let contents = std::fs::read(input_filename)?;
    let sexp = rsexp::from_slice(&contents)?;

Writing a sexp file can be done by first serializing the data to a buffer then writing this buffer out. Alternatively, the sexp.write(w)? function can be used to directly output the data to a w object that implements the Write trait.

    let data = sexp.to_bytes();
    std::fs::write(output_filename, data)?;

Conversion to/from Native Types

The OfSexp and SexpOf traits define some functions to convert a given type from/to a Sexp. These traits are implemented for most basic types, including maps. Two associated derive macros can be used to define these traits on structs and enums.

#[derive(OfSexp, SexpOf)]
struct StructXYZ {
    x: i64,
    y: Option<(i32, i32)>,
    z: String,
}

#[derive(OfSexp, SexpOf)]
enum Abc {
    A(StructXYZ),
    B { x: i64, z: String },
    C,
}


    let sexp = abc.sexp_of();
    let abc: Abc = sexp.of_sexp()?;

Intro: we are creating a software system for a pizza restaurant, one of the modules is supposed to handle the management of various pizza recipes and how the orders are put together, and a big part of the module will be the control of food types, the potential allergens in recipes, and calories counting.

rust_pizzeria Intro: we are creating a software system for a pizza restaurant, one of the modules is supposed to handle the management of various pizz

1 Oct 26, 2021

Comments

Add criterion microbenchmarks and optimize sexp_no_leading_blank.
This PR adds some microbenchmarks which generate different example sexps of different lengths, depths, number of characters per atom, and quoted/unquoted atoms.

These benchmarks were then used to optimize sexp_no_leading_blank. The main two changes are:

remove context() calls, saving a few % across the board.

replace nom::branch::alt in sexp_no_leading_blank with a rust-native if-condition.

The same optimization turns out not to improve things much in atom.

See report for details (tested on Intel Xeon Processor (Cascadelake), 2693 MHz via digitalocean). Also tested on Intel(R) Core(TM) i7-4850HQ CPU @ 2.30GHz with similar results.

Use this command to save a baseline (default name is base):

cargo bench --bench rsexp_benchmark -- --save-baseline

And this command to run comparing against a saved baseline:

cargo bench --bench rsexp_benchmark -- --baseline base
opened by AdamCanady 1