lens-regex-pcre

Hackage and Docs

• NOTE: I don't promise that this is fast yet, nor do I have any benchmarks;
• NOTE: currently only supports Text but should be generalizable to more string-likes; open an issue if you need it

Based on pcre-heavy; so it should support any regexes which it supports. I'll likely add a way to pass settings in soon; make an issue if you need this :)

Working with Regexes in Haskell kinda sucks; it's tough to figure out which libs to use, and even after you pick one it's tough to figure out how to use it.

As it turns out; regexes are a very lens-like tool; Traversals allow you to select and alter zero or more matches; traversals can even carry indexes so you know which match or group you're working on.

Note that all traversals in this library are not techically lawful, as the semantics of regular expressions don't allow for it; They break the 'multi-set' idempotence law of traversals (same one broken by filtered from lens); in reality this isn't usually a problem (I've literally never encountered an issue with it); but consider yourself warned. Test your code.

Here are a few examples:

txt :: Text
txt = "raindrops on roses and whiskers on kittens"

-- Search
λ> has (regex [rx|whisk|]) txt
True

-- Get matches
λ> txt ^.. regex [rx|\br\w+|] . match
["raindrops","roses"]

-- Edit matches
λ> txt & regex [rx|\br\w+|] . match %~ T.intersperse '-' . T.toUpper
"R-A-I-N-D-R-O-P-S on R-O-S-E-S and whiskers on kittens"

-- Get Groups
λ> txt ^.. regex [rx|(\w+) on (\w+)|] . groups
[["raindrops","roses"],["whiskers","kittens"]]

-- Edit Groups
λ> txt & regex [rx|(\w+) on (\w+)|] . groups %~ reverse
"roses on raindrops and kittens on whiskers"

-- Get the third match
λ> txt ^? iregex [rx|\w+|] . index 2 . match
Just "roses"

-- Match integers, 'Read' them into ints, then sort them in-place
-- dumping them back into the source text afterwards.
λ> "Monday: 29, Tuesday: 99, Wednesday: 3" 
   & partsOf (iregex [rx|\d+|] . match . unpacked . _Show @Int) %~ sort
"Monday: 3, Tuesday: 29, Wednesday: 99"

Basically anything you want to do is possible somehow.

Expected behaviour (and examples) can be found in the test suite:

describe "regex" $ do
    describe "match" $ do
        describe "getting" $ do
            it "should find one match" $ do
                "abc" ^.. regex [rx|b|] . match
                `shouldBe` ["b"]

            it "should find many matches" $ do
                "a b c" ^.. regex [rx|\w|] . match
                `shouldBe` ["a", "b", "c"]

            it "should fold" $ do
                "a b c" ^. regex [rx|\w|] . match
                `shouldBe` "abc"

            it "should match with a group" $ do
                "a b c" ^.. regex [rx|(\w)|] . match
                `shouldBe` ["a", "b", "c"]

            it "should match with many groups" $ do
                "a b c" ^.. regex [rx|(\w) (\w)|] . match
                `shouldBe` ["a b"]

            it "should be greedy when overlapping" $ do
                "abc" ^.. regex [rx|\w+|] . match
                `shouldBe`["abc"]

            it "should respect lazy modifiers" $ do
                "abc" ^.. regex [rx|\w+?|] . match
                `shouldBe`["a", "b", "c"]

        describe "setting" $ do
            it "should allow setting" $ do
                ("one two three" & regex [rx|two|] . match .~ "new")
                `shouldBe` "one new three"

            it "should allow setting many" $ do
                ("one <two> three" & regex [rx|\w+|] . match .~ "new")
                `shouldBe` "new <new> new"

            it "should allow mutating" $ do
                ("one two three" & regex [rx|two|] . match %~ (<> "!!"). T.toUpper)
                `shouldBe` "one TWO!! three"

            it "should allow mutating many" $ do
                ("one two three" & regex [rx|two|] . match %~ T.toUpper)
                `shouldBe` "one TWO three"

describe "iregex" $ do
    describe "match" $ do
        it "should allow folding with index" $ do
            ("one two three" ^.. (iregex [rx|\w+|] <. match) . withIndex)
            `shouldBe` [(0, "one"), (1, "two"), (2, "three")]

        it "should allow getting with index" $ do
            ("one two three" ^.. iregex [rx|\w+|] . index 1 . match)
            `shouldBe` ["two"]

        it "should allow setting with index" $ do
            ("one two three" & iregex [rx|\w+|] <. match .@~ T.pack . show)
            `shouldBe` "0 1 2"

        it "should allow mutating with index" $ do
            ("one two three" & iregex [rx|\w+|] <. match %@~ \i s -> (T.pack $ show i) <> ": " <> s)
            `shouldBe` "0: one 1: two 2: three"

describe "groups" $ do
    describe "getting" $ do
        it "should get groups" $ do
            "a b c" ^.. regex [rx|(\w)|] . groups
            `shouldBe` [["a"], ["b"], ["c"]]

        it "should get multiple groups" $ do
            "raindrops on roses and whiskers on kittens" ^.. regex [rx|(\w+) on (\w+)|] . groups
            `shouldBe` [["raindrops","roses"],["whiskers","kittens"]]

        it "should allow getting a specific index" $ do
            ("one two three four" ^.. regex [rx|(\w+) (\w+)|] . groups . ix 1)
            `shouldBe` ["two", "four"]

    describe "setting" $ do
        it "should allow setting groups as a list" $ do
            ("one two three" & regex [rx|(\w+) (\w+)|] . groups .~ ["1", "2"])
            `shouldBe` "1 2 three"

        it "should allow editing when result list is the same length" $ do
            ("raindrops on roses and whiskers on kittens" & regex [rx|(\w+) on (\w+)|] . groups %~ reverse)
            `shouldBe` "roses on raindrops and kittens on whiskers"

    describe "traversed" $ do
        it "should allow setting all group matches" $ do
            ("one two three" & regex [rx|(\w+) (\w+)|] . groups . traversed .~ "new")
            `shouldBe` "new new three"

        it "should allow mutating" $ do
            ("one two three four" & regex [rx|one (two) (three)|] . groups . traversed %~ (<> "!!") . T.toUpper)
            `shouldBe` "one TWO!! THREE!! four"

        it "should allow folding with index" $ do
            ("one two three four" ^.. regex [rx|(\w+) (\w+)|] . groups . traversed . withIndex)
            `shouldBe` [(0, "one"), (1, "two"), (0, "three"), (1, "four")]

        it "should allow setting with index" $ do
            ("one two three four" & regex [rx|(\w+) (\w+)|] . groups . traversed .@~ T.pack . show)
            `shouldBe` "0 1 0 1"

        it "should allow mutating with index" $ do
            ("one two three four" & regex [rx|(\w+) (\w+)|] . groups . traversed %@~ \i s -> (T.pack $ show i) <> ": " <> s)
            `shouldBe` "0: one 1: two 0: three 1: four"

        it "should compose indices with matches" $ do
            ("one two three four" ^.. (iregex [rx|(\w+) (\w+)|] <.> groups . traversed) . withIndex)
            `shouldBe` [((0, 0), "one"), ((0, 1), "two"), ((1, 0), "three"), ((1, 1), "four")]

describe "matchAndGroups" $ do
    it "should get match and groups" $ do
        "raindrops on roses and whiskers on kittens" ^.. regex [rx|(\w+) on (\w+)|] . matchAndGroups
        `shouldBe` [("raindrops on roses",["raindrops","roses"]),("whiskers on kittens",["whiskers","kittens"])]