Regex module

2 files changed, 103 insertions, 1 deletions

diff --git a/src/gleam/regex.gleam b/src/gleam/regex.gleam
new file mode 100644
index 0000000..3740984
--- /dev/null
+++ b/src/gleam/regex.gleam
@@ -0,0 +1,75 @@
+//// This module contains regular expression matching functions for strings.
+//// The matching algorithms of the library are based on the PCRE library, but not
+//// all of the PCRE library is interfaced and some parts of the library go beyond
+//// what PCRE offers. Currently PCRE version 8.40 (release date 2017-01-11) is used.
+
+pub external type Regex
+
+/// When a regular expression fails to compile:
+///
+/// - error — a descriptive error message
+/// - index — the index of the cause in the regex string
+///
+pub type FromStringError {
+  FromStringError(error: String, index: Int)
+}
+
+/// Create a new Regex.
+///
+/// ## Examples
+///
+///    > let Ok(re) = from_string("[0-9]")
+///    > match(re, "abc123")
+///    True
+///
+///    > match(re, "abcxyz")
+///    False
+///
+///    > from_string("[0-9")
+///    Error(
+///      FromStringError(
+///        error: "missing terminating ] for character class",
+///        index: 4
+///      )
+///    )
+///
+pub external fn from_string(String) -> Result(Regex, FromStringError) =
+  "gleam_stdlib" "regex_from_string"
+
+pub type Options {
+  Options(case_insensitive: Bool, multi_line: Bool)
+}
+
+/// Create a Regex with some additional options.
+///
+/// ## Examples
+///
+///    > let options = Options(case_insensitive: False, multi_line: True)
+///    > let Ok(re) = from_string_with(options, "^[0-9]")
+///    > match(re, "abc\n123")
+///    True
+///
+///    > let options = Options(case_insensitive: True, multi_line: False)
+///    > let Ok(re) = from_string_with(options, "[A-Z]")
+///    > match(re, "abc123")
+///    True
+///
+pub external fn from_string_with(
+  Options,
+  String,
+) -> Result(Regex, FromStringError) =
+  "gleam_stdlib" "regex_from_string_with"
+
+/// Returns a boolean indicating whether there was a match or not.
+///
+/// ## Examples
+///
+///    > let Ok(re) = from_string("^f.o.?")
+///    > match(re, "foo")
+///    True
+///
+///    > match(re, "boo")
+///    False
+///
+pub external fn match(Regex, String) -> Bool =
+  "gleam_stdlib" "regex_match"
diff --git a/src/gleam_stdlib.erl b/src/gleam_stdlib.erl
index 4b9c6a1..f0adbd0 100644
--- a/src/gleam_stdlib.erl
+++ b/src/gleam_stdlib.erl
@@ -10,7 +10,8 @@
          string_pop_grapheme/1, string_starts_with/2, string_ends_with/2,
          string_pad/4, decode_tuple2/1, decode_map/1, bit_string_int_to_u32/1,
          bit_string_int_from_u32/1, bit_string_append/2, bit_string_part_/3,
-         decode_bit_string/1]).
+         decode_bit_string/1, regex_from_string/1, regex_from_string_with/2,
+         regex_match/2]).
 
 should_equal(Actual, Expected) -> ?assertEqual(Expected, Actual).
 should_not_equal(Actual, Expected) -> ?assertNotEqual(Expected, Actual).
@@ -162,3 +163,29 @@ bit_string_int_from_u32(<<I:32>>) ->
   {ok, I};
 bit_string_int_from_u32(_) ->
   {error, nil}.
+
+regex_from_string_with_opts(Options, String) ->
+    case re:compile(String, Options) of
+        {ok, MP} -> {ok, MP};
+        {error, {Str, Pos}} ->
+            {error, {from_string_error, unicode:characters_to_binary(Str), Pos}}
+    end.
+
+regex_from_string(String) ->
+    regex_from_string_with_opts([unicode], String).
+
+regex_from_string_with(Options, String) ->
+    OptList = case Options of
+        {options, true, _} -> [unicode, caseless];
+        _ -> [unicode]
+    end,
+    case Options of
+        {options, _, true} -> regex_from_string_with_opts([multiline | OptList], String);
+        _ -> regex_from_string_with_opts(OptList, String)
+    end.
+
+regex_match(Regex, String) ->
+    case re:run(String, Regex) of
+        {match, _} -> true;
+        _ -> false
+    end.