feat: add PairSwap, PairBoth

fun/pair.go

@@ -14,3 +14,14 @@ func PairV1[A any, B any](p Pair[A, B]) A { return p.V1 }
 
 // PairV2 returns the second element of the pair.
 func PairV2[A any, B any](p Pair[A, B]) B { return p.V2 }
+
+// PairBoth returns both parts of the pair.
+func PairBoth[A any, B any](p Pair[A, B]) (A, B) {
+	return p.V1, p.V2
+}
+
+// PairSwap returns a pair with swapped parts.
+func PairSwap[A any, B any](p Pair[A, B]) Pair[B, A] {
+	a, b := PairBoth(p)
+	return NewPair(b, a)
+}

fun/pair_test.go

@@ -0,0 +1,14 @@
+package fun_test
+
+import (
+	"testing"
+
+	"github.com/primetalk/goio/fun"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPairBoth(t *testing.T) {
+	one, a := fun.PairBoth(fun.NewPair(1, "A"))
+	assert.Equal(t, 1, one)
+	assert.Equal(t, "A", a)
+}