add lets.Val(...) function

lets/lets.go

@@ -13,3 +13,11 @@ func If[T any](condition bool, trueVal, falseVal T) T {
 	}
 	return falseVal
 }
+
+// Val[T] return s[0] if s is give or else return v
+func Val[T any](v T, s ...T) T {
+	if len(s) > 0 {
+		return s[0]
+	}
+	return v
+}

lets/lets_test.go

@@ -2,10 +2,12 @@
 // Use of this source code is governed by Apache License 2.0 that
 // can be found in the LICENSE file.
 
-package lets
+package lets_test
 
 import (
 	"testing"
+
+	"github.com/alimy/tryst/lets"
 )
 
 func TestIf(t *testing.T) {
@@ -18,8 +20,24 @@ func TestIf(t *testing.T) {
 		{true, 1, 2, 1},
 		{false, 1, 2, 2},
 	} {
-		if res := If(tc.condition, tc.trueVal, tc.falseVal); res != tc.result {
+		if res := lets.If(tc.condition, tc.trueVal, tc.falseVal); res != tc.result {
 			t.Errorf("If(%t, %d, %d) want %d but got %d", tc.condition, tc.trueVal, tc.falseVal, tc.result, res)
 		}
 	}
 }
+
+func TestVal(t *testing.T) {
+	for _, tc := range []struct {
+		v int
+		s []int
+		r int
+	}{
+		{4, []int{5, 6}, 5},
+		{4, []int{5}, 5},
+		{5, []int{}, 5},
+	} {
+		if res := lets.Val(tc.v, tc.s...); res != tc.r {
+			t.Errorf("give v:%d s:%+v want: %d but got %d", tc.v, tc.s, tc.r, res)
+		}
+	}
+}