add options.Map()

2 files changed, 16 insertions, 1 deletions

diff --git a/options/options.go b/options/options.go
index 9754e2d..bfae710 100644
--- a/options/options.go
+++ b/options/options.go
@@ -21,10 +21,19 @@ func FromPointer[T any](value *T) Option[T] {
 	}
 }
 
-// IsNoneOrZero returns whether the Option is either empty, or contains a zero value.
+// IsNoneOrZero returns whether o is either empty, or contains a zero value.
 func IsNoneOrZero[T comparable](o Option[T]) bool {
 	return o.IsNoneOr(func(value T) bool {
 		var zero T
 		return zero == value
 	})
 }
+
+// Map applies the given function to the value contained in o, if there is one.
+func Map[T, U any](o Option[T], mapping func(T) U) Option[U] {
+	if t, ok := o.Unpack(); ok {
+		return Some(mapping(t))
+	} else {
+		return None[U]()
+	}
+}
diff --git a/options/options_test.go b/options/options_test.go
index 9947b9d..caeb303 100644
--- a/options/options_test.go
+++ b/options/options_test.go
@@ -7,6 +7,7 @@
 package options
 
 import (
+	"strconv"
 	"testing"
 
 	. "github.com/majewsky/gg/internal/test"
@@ -23,3 +24,8 @@ func TestIsNoneOrZero(t *testing.T) {
 	AssertEqual(t, IsNoneOrZero(Some(0)), true)
 	AssertEqual(t, IsNoneOrZero(Some(1)), false)
 }
+
+func TestMap(t *testing.T) {
+	AssertEqual(t, Map(None[int](), strconv.Itoa), None[string]())
+	AssertEqual(t, Map(Some(42), strconv.Itoa), Some("42"))
+}