【Rust日报】2021-11-27 yap：一个小型的、基于迭代器的、零依赖的解析库

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Rena的内存模型

Rena是我在Rust中实现的Lox语言的树遍历解释器。我用rust重写它，以熟悉rust的borrow checker和提供的各种工具链。

在这篇文章中，我将解释我如何为解释器实现一个简单的环境。

Gitlab 链接，https://github.com/veera-sivarajan/rena

文章链接，https://veera.app/rena's_memory_model.html

yap：一个小型的、基于迭代器的、零依赖的解析库

Yap是一个小型的、零依赖的解释器库，灵感来自于parser-combinator。我试图以简洁性换取简单性，并以迭代器接口的灵活性为基础。它的目标是使解析字符串和切片变得容易，并且易于使用。

在过去的几个星期里，我一直在构建和使用它，我认为它已经准备好向其他可能有兴趣使用它的人发布了!

下面是它的用法:

use yap::{ // This trait has all of the parsing methods on it:Tokens,// Allows you to use `.into_tokens()` on strings and slices, // to get an instance of the above:IntoTokens
};// Step 1: convert our input into something implementing `Tokens`
// ================================================================let mut tokens = "10 + 2 x 12-4,foobar".into_tokens();// Step 2: Parse some things from our tokens
// =========================================#[derive(PartialEq,Debug)]
enum Op { Plus, Minus, Multiply }
#[derive(PartialEq,Debug)]
enum OpOrDigit { Op(Op), Digit(u32) }// The `Tokens` trait builds on `Iterator`, so we get a `next` method.
fn parse_op(t: &mut impl Tokens<Item=char>) -> Option<Op> {match t.next()? {'-' => Some(Op::Minus),'+' => Some(Op::Plus),'x' => Some(Op::Multiply),_ => None}
}// We also get other useful functions..
fn parse_digits(t: &mut impl Tokens<Item=char>) -> Option<u32> {let s: String = t.tokens_while(|c| c.is_digit(10)).collect();s.parse().ok()
}// As well as combinator functions like `sep_by_all` and `surrounded_by`..
let op_or_digit = tokens.sep_by_all(|t| t.surrounded_by(|t| parse_digits(t).map(OpOrDigit::Digit),|t| { t.skip_tokens_while(|c| c.is_ascii_whitespace()); }), |t| parse_op(t).map(OpOrDigit::Op)
);// Now we've parsed our input into OpOrDigits, let's calculate the result..
let mut current_op = Op::Plus;
let mut current_digit = 0;
for d in op_or_digit {match d {OpOrDigit::Op(op) => {current_op = op },OpOrDigit::Digit(n) => {match current_op {Op::Plus => { current_digit += n },Op::Minus => { current_digit -= n },Op::Multiply => { current_digit *= n },}},}
}
assert_eq!(current_digit, 140);// Step 3: do whatever you like with the rest of the input!
// ========================================================// This is available on the concrete type that strings
// are converted into (rather than on the `Tokens` trait):
let remaining = tokens.remaining();assert_eq!(remaining, ",foobar");

Gitlab 链接，https://github.com/jsdw/yap

文章链接，https://www.reddit.com/r/rust/comments/r3blx1/announcing_yap_a_small_iterator_based_zero/