126 lines
4.2 KiB
Elm
126 lines
4.2 KiB
Elm
module Regex where
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{-| A library for working with regular expressions. It uses [the
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same kind of regular expressions accepted by JavaScript](https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions).
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# Create
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@docs regex, escape, caseInsensitive
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# Helpful Data Structures
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These data structures are needed to help define functions like [`find`](#find)
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and [`replace`](#replace).
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@docs HowMany, Match
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# Use
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@docs contains, find, replace, split
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-}
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import Maybe (Maybe)
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import Native.Regex
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data Regex = Regex
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{-| Escape strings to be regular expressions, making all special characters
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safe. So `regex (escape "^a+")` will match exactly `"^a+"` instead of a series
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of `a`’s that start at the beginning of the line.
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-}
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escape : String -> String
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escape = Native.Regex.escape
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{-| Create a Regex that matches patterns [as specified in JavaScript](https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions#Writing_a_Regular_Expression_Pattern).
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Be careful to escape backslashes properly! For example, `"\w"` is escaping the
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letter `w` which is probably not what you want. You probably want `"\\w"`
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instead, which escapes the backslash.
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-}
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regex : String -> Regex
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regex = Native.Regex.regex
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{-| Make a regex case insensitive -}
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caseInsensitive : Regex -> Regex
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caseInsensitive = Native.Regex.caseInsensitive
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{-| Check to see if a Regex is contained in a string.
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```haskell
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contains (regex "123") "12345" == True
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contains (regex "b+") "aabbcc" == True
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contains (regex "789") "12345" == False
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contains (regex "z+") "aabbcc" == False
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```
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-}
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contains : Regex -> String -> Bool
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contains = Native.Regex.contains
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{-| A `Match` represents all of the details about a particular match in a string.
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Here are details on each field:
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* `match` — the full string of the match.
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* `submatches` — a regex might have [subpatterns, surrounded by
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parentheses](https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions#Using_Parenthesized_Substring_Matches).
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If there are N subpatterns, there will be N elements in the `submatches` list.
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Each submatch in this list is a `Maybe` because not all subpatterns may trigger.
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For example, `(regex "(a+)|(b+)")` will either match many `a`’s or
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many `b`’s, but never both.
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* `index` — the index of the match in the original string.
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* `number` — if you find many matches, you can think of each one
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as being labeled with a `number` starting at one. So the first time you
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find a match, that is match `number` one. Second time is match `number` two.
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This is useful when paired with `replace All` if replacement is dependent on how
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many times a pattern has appeared before.
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-}
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type Match = { match : String, submatches : [Maybe String], index : Int, number : Int }
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{-| `HowMany` is used to specify how many matches you want to make. So
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`replace All` would replace every match, but `replace (AtMost 2)` would
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replace at most two matches (i.e. zero, one, two, but never three or more).
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-}
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data HowMany = All | AtMost Int
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{-| Find matches in a string:
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```haskell
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findTwoCommas = find (AtMost 2) (regex ",")
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-- map .index (findTwoCommas "a,b,c,d,e") == [1,3]
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-- map .index (findTwoCommas "a b c d e") == []
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places = find All (regex "[oi]n a (\\w+)") "I am on a boat in a lake."
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-- map .match places == ["on a boat", "in a lake"]
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-- map .submatches places == [ [Just "boat"], [Just "lake"] ]
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```
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-}
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find : HowMany -> Regex -> String -> [Match]
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find = Native.Regex.find
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{-| Replace matches. The function from `Match` to `String` lets
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you use the details of a specific match when making replacements.
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```haskell
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devowel = replace All (regex "[aeiou]") (\_ -> "")
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-- devowel "The quick brown fox" == "Th qck brwn fx"
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reverseWords = replace All (regex "\\w+") (\{match} -> String.reverse match)
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-- reverseWords "deliver mined parts" == "reviled denim strap"
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```
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-}
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replace : HowMany -> Regex -> (Match -> String) -> String -> String
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replace = Native.Regex.replace
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{-| Split a string, using the regex as the separator.
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```haskell
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split (AtMost 1) (regex ",") "tom,99,90,85" == ["tom","99,90,85"]
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split All (regex ",") "a,b,c,d" == ["a","b","c","d"]
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```
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-}
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split : HowMany -> Regex -> String -> [String]
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split = Native.Regex.split
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