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https://github.com/AbhinavOmprakash/luna

A DSL that translates to regex
https://github.com/AbhinavOmprakash/luna

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A DSL that translates to regex

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# luna

[![Clojars Project](https://img.shields.io/clojars/v/org.clojars.abhinav/luna.svg)](https://clojars.org/org.clojars.abhinav/luna)

[![codecov](https://codecov.io/gh/AbhinavOmprakash/luna/branch/master/graph/badge.svg?token=40ZSIXXSE3)](https://codecov.io/gh/AbhinavOmprakash/luna)



No more regrets, wield the power of regex with the readability of English with luna.



# About



luna is a Domain specific language (DSL) that is readable and translates into a `Regex.Pattern` object. luna is still in

Beta but don't let this discourage you from using it, it has a good test suite and bug reports are key to improving it.



# Why?



Readable code can be hard to maintain. Unreadable code can be impossible to maintain.



# Installing and Using

add this to your project.clj file

```clojure

:dependencies [[org.clojars.abhinav/luna "0.1.0-SNAPSHOT"]]

```

Luna has one function `pre` that does the heavy lifting.

```clojure

;; import it

(ns user.core

  (:require [luna.core :as luna]))



(luna/pre [:match ["x" :digits :atleast 4 :times] :when :at-start])

;;=> #"^x\d{4,}"

```

# Contributing



I welcome contributions, even from first-timers. Feedbacks and suggestions are welcome too.



## If you'd like to contribute but don't know how



### Test cases



The easiest thing you can do to contribute is write a test case, this project can never have too many test cases.



### Documentation



Documentation is very important, more so than the code in the project, so I value these contributions highly. There will

be some parts (hopefully not a lot) of the documentation that may not make sense, or maybe wrong, or can be worded

differently.



### Refactoring



I welcome refactors like



- Variable and function renaming.

- Extracting functions.

- Moving things around to make more sense.



# Grammar/language



the `pre` function is used to parse the dsl and return a `regex.Pattern` object.



the arguments to `pre` can be plain strings, or vectors, or a `Pattern` object.



```clojure

=> (pre "xy")

#"xy"

; pre can take multiple args

=> (pre "a" #"b" [:match "c" :when :at-start])

#"ab^c"

```



The first element in the vector determines how the rest is processed. There are two main and commonly used

keywords `:match` (or `:m`) and `:capture` (or `:c`) that are valid first elements.



```clojure

=> (pre [:match "xy"])

#"xy"

=> (pre [:capture "xy"])

#"(xy)"

```



The next element is either a string or a vector, containing character classes. The valid syntax of the vector depends on

whether `:match` or `:capture` was used.



## character class syntax for `:match`



to be used as



```clojure

[:match ["xy"]]



;;      ----char-class vector----

[:match ["x" :when :at-start "y"]]

```



I will omit `[:match ...]` for brevity.



examples of valid char-class vector



```clojure

;; by default the elements in the char-class vector are evaluate to a string and separated by | in match

["xy"] => #"xy"

["x" "y"] => #"x|y"

["x" "y" "z"] => #"x|y|z"



;; if you would prefer to concatenate them, then use a nested vector

[["x" "y" "z"]] => #"xyz"



;; using ranges in character classes

[[1 :to 7]] => #"[1-7]"

[1 [2 :to 5]] => #"[1[2-5]]"



;; using anchors inside vector

["x" :when :at-start] => #"^x"

["x" :when :at-start "y"] => #"^xy"



;; using quantifiers inside vector

["x" :atleast 5 :times "y"] => #"x{5,}y"



;; the :times can be omitted but helps with readability

["x" :atleast 5 "y"] => #"x{5,}y"



;;combining anchors and quantifiers

["x" :atleast 5 :times :when :at-start "y"] => #"^x{5,}y"

```



# after the character class vector we have modifiers.



```clojure

;;             -modifiers-

[:match ["xy"] :atleast 2] => #"xy{2,}"

;;             ---modifiers---

[:match ["xy"] :when :at-start] => #"^xy"



```



Note! if you're using quantifiers and/or anchors inside the character class vector

**and** outside then the result will be a "match everything enclosed"

here's an example



```clojure

[:match ["x" :atleast 5 "y"] :atleast 2] => #"(?:x{5}y){2}"

```



# :match-enc



`:match-enc[closed]`

by default

`[:match ["x" :atleast 5 "y"] ]` yields `#"x{5}|y"`

instead if you want `#"(?:x{5}|y)`

use :match-enc



```clojure

[:match-enc ["x" :atleast 5 "y"]] => #"(?:x{5}y)"

```



# sets



if you wish to use set constructs like negation `[^abc]` or intersection `[abc&&[ab]]`

you can use clojure's literal set notation



```clojure

; negation

[:match #{:not "abc"}] => #"[^abc]"

[:match #{:not "abc" :upper [1 :to 5]}] => #"[^abcA-Z1-5]"



;; intersection

[:match #{:and "abc" "ab"}] => #"[abc&&[ab]]"

[:match #{:and "abc" :upper [1 :to 4]}] => #"[abc&&[A-Z]&&[1-4]]"



; combining both

[:match #{:and "abc" #{:not "ab" :digits}}] => #"[abc&&[^ab1-9]]"

```



# capture



the syntax of capture is similar to `:match`



## Anchors



### Match



```clojure

[:match "x" :when :at-start] ; #"^x"

[:match "xy" :when :at-start] ; #"^xy"

[:match ["xy"] :when :at-start] ; #"^xy"

[:match ["x" :or "y"] :when :at-start] ; #"^x|y"

[:match ["x" :when :at-start :or "y"]] ; #"^x|y"



[:match [:digits] :when :at-end] ; #"\d$"

```



### Capture



```clojure

[:capture "x" :when :at-start] ; #"^(x)"

[:capture "xy" :when :at-start] ; #"^(xy)"

[:capture ["x" "y"] :when :at-start] ; #"^(xy)"

[:capture [["x" "y"]] :when :at-start] ; #"^([xy])"



[:capture :digits :when :at-end] ; #"$(\d)"

[:capture "x" :when :at-word-start] ; #"\b(x)"

[:capture "x" :when :not :at-word-start] ; #"\B(x)"

```



## Group constructs



### assertions



```clojure

;; lookahead positive and negative

[:match "x" :when :before "y"] ; #"x(?=y)"

[:match "x" :when :not-before "y"] ; #"x(?!y)"



;; lookbehind positive and negative

[:match "x" :when :after "y"] ; #"(?<=y)x"

[:match "x" :when :not-after "y"] ; #"(?)[\s\S]*?(?=<)"

(pre

  [:match [:everything] :lazily :between ">" :and "<"])



#"^[A-Z]{1,2}[0-9R][0-9A-Z]?[0-9][ABD-HJLNP-UW-Z]{2}$"

(pre [:m :upper :between 1 :and 2 :when :at-start]

     [:m [[[0 :to 9] "R"]]]

     [:m [[[0 :to 9] :upper]] :0-or-1]

     [:m [[[0 :to 9]]]]

     [:m [["AB" ["D" :to "H"] "JLN" ["P" :to "U"] ["W" :to "Z"]]]

      :atleast 2 :when :at-end])



```