Support regexp match filtering

Author: BooleanCat

it/filter/filter.go

@@ -1,7 +1,10 @@
 // This package contains functions intended for use with [iter.Filter].
 package filter
 
-import "cmp"
+import (
+	"cmp"
+	"regexp"
+)
 
 // IsEven returns true when the provided integer is even.
 func IsEven[T ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr | ~int | ~int8 | ~int16 | ~int32 | ~int64](integer T) bool {
@@ -95,3 +98,9 @@ func Or[T any](filters ...func(T) bool) func(T) bool {
 		return false
 	}
 }
+
+func Match[T string | []byte](pattern *regexp.Regexp) func(T) bool {
+	return func(term T) bool {
+		return pattern.MatchString(string(term))
+	}
+}

it/filter/filter_test.go

@@ -3,6 +3,7 @@ package filter_test
 import (
 	"fmt"
 	"maps"
+	"regexp"
 	"slices"
 
 	"github.com/BooleanCat/go-functional/v2/it"
@@ -129,3 +130,27 @@ func ExampleOr() {
 	// 2
 	// 4
 }
+
+func ExampleMatch_string() {
+	pattern := regexp.MustCompile(`^foo`)
+
+	strings := slices.Values([]string{"foobar", "barfoo"})
+
+	for match := range it.Filter(strings, filter.Match[string](pattern)) {
+		fmt.Println(match)
+	}
+
+	// Output: foobar
+}
+
+func ExampleMatch_bytes() {
+	pattern := regexp.MustCompile(`^foo`)
+
+	strings := slices.Values([][]byte{[]byte("foobar"), []byte("barfoo")})
+
+	for match := range it.Filter(strings, filter.Match[[]byte](pattern)) {
+		fmt.Println(string(match))
+	}
+
+	// Output: foobar
+}