Rust nom

Its goal is to provide tools rust nom build safe parsers without compromising the speed or memory consumption. To that end, it uses extensively Rust's strong typing and memory safety to produce fast and correct parsers, and provides functions, macros and traits to abstract most of the error prone plumbing. Hexadecimal color parser:. Compared to the usual handwritten C parsers, nom parsers are just as fast, rust nom, free from buffer overflow vulnerabilities, and handle common patterns for you:.

Welcome to Nominomicon; a guide to using the Nom parser for great good. This guide will give you an introduction to the theory and practice of using Nom. By combining parsers with combinators, you can build complex parsers up from simpler ones. Introduction 1. The Nom Way 2.

Rust nom

This tutorial is a guide to parsing with nom. It covers the basics of parsing and how to use nom to parse a string into a data structure. We will cover a variety of different examples ranging from parsing simple CSS like syntax to a full blown Markdown parser. If you would like to get involved in an open source project and like Rust crates, we welcome your contributions to the r3bl-open-core repo. For more information on general Rust type system design functional approach rather than object oriented , please take a look at this paper by Will Crichton demonstrating Typed Design Patterns with Rust. This tutorial takes a hands on approach to learning nom. However, the resources listed below are very useful for learning nom. Think of them as a reference guide and deep dive into how the nom library works. You can write small functions that parse a specific part of your input, and then combine them to build a parser that parses the whole input. Roughly the way it works is that you tell nom how to parse a bunch of bytes in a way that matches some pattern that is valid for your data. It will try to parse as much as it can from the input, and the rest of the input will be returned to you.

HexDisplay std. The basic things you need to know - first, Nom is macros all the way down, and second, Nom prefers to work with byte slices, not strings. Rust nom met pairs!

Nom , documented here is a parser library for Rust which is well worth the initial time investment. Likewise, for configuration files use dedicated parsers like ini or toml. But if the text is not regular, or some made-up format, then you need to scan that text without writing a lot of tedious string-processing code. The suggested go-to is often regex , but regexes can be frustratingly opaque when sufficiently involved. Nom provides a way to parse text which is just as powerful and can be built up by combining simpler parsers. If you ever had the itch to write your own programming language, Nom is a good place for you start on that hard road to obscurity.

I've been working on my new Rust side-project for several months now , and I've got some learnings to share. The project is called pq - it's a command-line tool to parse and query log files as time series. It comes with its own domain-specific language that is highly influenced by PromQL. A typical pq usage may look like this:. But surprisingly or not, about half of the time I've put into this project so far was dedicated to writing the parser of the pq 's own query language. To be honest, when I was starting the project, I didn't see that coming Luckily, writing a parser in Rust was mostly a pleasant experience, thanks to a crate concisely named nom. Although learning how to write parsers with nom wasn't completely seamless.

Rust nom

Parser combinators are higher-order functions that can accept several parsers as input and return a new parser as its output. This approach enables you to build parsers for simple tasks, such as parsing a certain string or a number, and compose them using combinator functions into a whole recursive descent parser. Benefits of combinatory parsing include testability, maintainability, and readability; each moving part is rather small and self-isolated, making the whole parser a composition of modular components. Yup, all we need is the nom library in the latest version 6. The fields are arranged according to the order in which they occur in a regular URI.

Figtree gourmet kitchen

And for now factors are just floating-point numbers:! Here I'll throw caution to the winds and throw away the error:! Clearly we need to understand this IResult type to go further, but first let's compare this with the regex solution:. Nom provides a way to parse text which is just as powerful and can be built up by combining simpler parsers. Instead of writing the grammar in a separate file and generating the corresponding code, you use very small functions with very specific purpose, like "take 5 bytes", or "recognize the word 'HTTP'", and assemble them in meaningful patterns like "recognize 'HTTP', then a space, then a version". A list of not yet implemented formats is available here. When we aren't interested in the intermediate results, but just want all the matching input, then recognize! Branches Tags. From line based formats like CSV, to more complex, nested formats such as JSON, nom can manage it, and provides you with useful tools:. This function takes a byte array as input, and tries to consume 4 bytes. You can build up your complicated parsers from simpler parsers, which you can test individually. Note that the body of our converting function has exactly the same code; the actual conversion depends on the return type of the function. If one branch fails, it tries the next, and returns the result of the first parser that succeeds:. Latest commit History 2, Commits. This is the great power of Nom, and it's why it's called a "parser combinator library".

It conjures visions of obscure grammars fed into arcane tools to generate thousands of lines of unreadable code.

While a lot of formats and the code handling them assume that they can fit the complete data in memory, there are formats for which we only get a part of the data at once, like network formats, or huge files. The pair! By combining parsers with combinators, you can build complex parsers up from simpler ones. Nom provides a function digit which matches a series of numerical digits. Notice that it was straightforward to combine an existing parser for greetings with a parser that picks up names, and then it was easy to make that name optional. The first result is the whole string, the second is the matched capture. Think of them as a reference guide and deep dive into how the nom library works. This is a very simple example, but it shows how you can combine parsers together to create more complex parsers. Latest commit History 2, Commits. Equivalent From implementation to avoid orphan rules in bits parsers.