BenchmarksForPosterity.01.cs

public static Verifier Combine(params Verifier[] verifiers) =>
  expression =>
  {
    var current = Init;
    foreach (var verify in verifiers)
    {
      var next = verify(expression);
      current = next.Apply(current.Apply(KeepRight));
    }
    return current;
  };

public static Verifier Combine2(params Verifier[] verifiers) =>
    expression => from xs in verifiers.TraverseA(v => v(expression))
                  select Unit.Default;

BenchmarksForPosterity.02.cs

|   Method | VCount |       Mean | Ratio |  Gen 0 | Allocated |
|--------- |------- |-----------:|------:|-------:|----------:|
|  Combine |      2 |   163.5 ns |  1.00 |      - |         - |
| Combine2 |      2 |   346.0 ns |  2.63 | 0.2828 |     592 B |
|          |        |            |       |        |           |
|  Combine |     10 | 1,206.3 ns |  1.00 |      - |         - |
| Combine2 |     10 | 2,425.0 ns |  2.03 | 1.0452 |    2192 B |

BenchmarksForPosterity.03.cs

/// <summary>
/// Combines verifiers
/// </summary>
/// <remark>
/// |               Method | VCount |       Mean | Ratio |  Gen 0 | Allocated |
/// |--------------------- |------- |-----------:|------:|-------:|----------:|
/// |          ThisCombine |      2 |   163.5 ns |  1.00 |      - |         - |
/// | CombineWithTraverseA |      2 |   346.0 ns |  2.63 | 0.2828 |     592 B |
/// |                      |        |            |       |        |           |
/// |          ThisCombine |     10 | 1,206.3 ns |  1.00 |      - |         - |
/// | CombineWithTraverseA |     10 | 2,425.0 ns |  2.03 | 1.0452 |    2192 B |
/// 
/// </remark>
/// <param name="verifiers">The verifiers to combine.</param>
public static Verifier Combine(params Verifier[] verifiers) =>
    expression =>
    {
        var current = Init;
        foreach (var verify in verifiers)
        {
            var next = verify(expression);
            current = next.Apply(current.Apply(KeepRight));
        }

        return current;
    };

BenchmarksForPosterity.04.cs

// ... _combineWithTraverseA = CombineWithTraverseA(sampleVerifiers);

/// <summary>
/// The combine method using TraverseA.
/// </summary>
[Benchmark]
public Validation<string, Unit> CombineWithTraverseA()
{
    return _combineWithTraverseA(_expression);
}

private static Verifier CombineWithTraverseA(params Verifier[] verifiers) =>
    expression => from xs in verifiers.TraverseA(v => v(expression))
                  select Unit.Default;