21–30 of 74 posts
"A Parser for Things
Is a function from Strings
To Lists of Pairs
Of Things and Strings!"
- Fritz RuehrConsider the most basic parsers you might want. For instance, a parser that only succeeds if it matches a string exactly, a parser that matches any single character and always succeeds, a parser that matches nothing and returns some constant, a parser that always fails. They're all simple and stupid and let's give them names: string("foobar") : Parser char : Parser always (x: A): Parser never : Parser These are parse…
There is a nice paper on the subject by Graham Hutton and Erik Meijer. It's a very good introduction to both parser combinators and monads, and it's very readable even for beginners.
Gotta love Parsec for Haskell and pyparsing for Python. Some other awesome parsing libs: PEGTL - C++ Parsing Expression Grammar Template Library https://github.com/taocpp/PEGTL Parboiled - Java & Scala PEG Library https://github.com/sirthias/parboiled Nom - Rust parser combinator framework https://github.com/Geal/nom Nearley - JavaScript parser toolkit https://github.com/Hardmath123/nearley Neotoma - Erlang library a…
check out Chevrotain
Let's rant a little: why the fuck can't you use some darker color for your text? Fucking tired of no-contrast website which are a pain to read. I hate having to use a DOM inspector to change some color to #000 so I can see if the content is useful. I guess I should be happy it is not an only-js blog.
Consider the most basic parsers you might want. For instance, a parser that only succeeds if it matches a string exactly, a parser that matches any single character and always succeeds, a parser that matches nothing and returns some constant, a parser that always fails. They're all simple and stupid and let's give them names: string("foobar") : Parser char : Parser always (x: A): Parser never : Parser These are parse…
Monadic parser combinators! There is a nice paper on the subject by Graham Hutton and Erik Meijer. It's a very good introduction to both parser combinators and monads, and it's very readable even for beginners.
type Parser t = Input -> Maybe (t, Input)
For anyone following along at home: think function which takes input + current position and may return: "Nothing" if the parser doesn't match, or "a value of type t along with the rest of the unparsed input".
(Obviously it'd have to be expanded to support errors properly, etc.)
EDIT: Of course, I guess you could argue that they just are monadic by definition since chaining using function composition and parameter passing is the essence of a monad... Maybe that's what you were driving at?
Slightly off-topic but please stop this js smooth scroll nonsense. If I wanted to use smooth scroll I would have enabled it in my browser.
Let's rant a little: why the fuck can't you use some darker color for your text? Fucking tired of no-contrast website which are a pain to read. I hate having to use a DOM inspector to change some color to #000 so I can see if the content is useful. I guess I should be happy it is not an only-js blog.
I will admit I don't find the letter spacing on that font to be particularly pleasant, and if you turn the "Cantarell" declaration off, it does become easier to read (better letter spacing and thicker strokes, which latter contributes positively to the contrast).
A few years ago I worked on a similar kind of project as part of my bachelors. We were converting SQL for Oracle to SQL for Microsoft SQL Server. One problem is dealing with features which language A supports and language B doesn't. Another problem is that it is a huge amount of work to match all syntax elements as well as all library usages. In fact, I guess it's not a good thing to say on HackerNews, but isn't it b…
I had a similar problem a few months ago with a Golang application that uses Postgres in production, but SQLite for unit tests. Since Go's SQL support has pluggable driver backends, I made a generic proxy driver [1] that can rewrite the incoming query, and used that in my application to rewrite from Postgres to SQLite syntax [2].
[1] https://godoc.org/github.com/majewsky/sqlproxy
[2] https://github.com/sapcc/limes/blob/205f9980a41d75fc0315e0ac...
Consider the most basic parsers you might want. For instance, a parser that only succeeds if it matches a string exactly, a parser that matches any single character and always succeeds, a parser that matches nothing and returns some constant, a parser that always fails. They're all simple and stupid and let's give them names: string("foobar") : Parser char : Parser always (x: A): Parser never : Parser These are parse…
I suspect these combinators are not very powerful compared to e.g. LR(k) parsers, and provide a false sense of modularity. (E.g. a minor grammar change leading to a large scale rewrite).
Let's rant a little: why the fuck can't you use some darker color for your text? Fucking tired of no-contrast website which are a pain to read. I hate having to use a DOM inspector to change some color to #000 so I can see if the content is useful. I guess I should be happy it is not an only-js blog.
Not sure what you mean? Its nearly black?