A Parser Combinator Library in Clojure
A Parser is a function that takes a char stream as an argument, for example string, and returns the parsed character/characters and rest of the char stream. From Clojure's POV, it looks something like this:
(def parser
(fn [char-stream]
;; Do something with the char-stream to parse a value
(vector value char-stream-state))) ;; updated char-stream as [buf pos end]
;; buf is a vector of charactersA Parser Combinator, on the other hand, is a higher order function (a function that takes other functions as an argument, for example, map, filter) that takes A Parser (A function) as an argument and returns another Parser. In that sense, A Parser Combinator is something that operates on Parsers. A few examples of Parser Combinators on this library can be - choice, between, optional, many*, many+ etc. Lets see an example.
(ns examples.readme-example
(:require [jdsl.char-parser :as jp]
[jdsl.char-stream :as cs]
[jdsl.basic :as jb]
[jdsl.combinator :refer [between many*]]))
(def any-char-within-braces
(-> (many* jp/alpha-num)
(between (jp/char \[) (jp/char \]))))
(try
(jb/run any-char-within-braces (cs/create "[abcd123]"))
(catch clojure.lang.ExceptionInfo e
(jb/print-error e)))
;; returns [
;; [\a \b \c \d \1 \2 \3] as parsed value
;; [\[ \a \b \c \d \1 \2 \3 \] 8 9] as final char stream state
;; ]
;; final char-stream state
;; buf = [\[ \a \b \c \d \1 \2 \3 \]
;; pos = 8
;; end = 9