docs/csharp/language-reference/operators/snippets/shared/BooleanLogicalOperators.cs - main - aprogrammer/dotnet-docs

docs/csharp/language-reference/operators/snippets/shared/BooleanLogicalOperators.cs
186 строк5 KB
Bill Wagner
first draft of nameof updates (#29549)
15 июн 2022, 00:43
15 июн 2022, 00:4386ba43a
namespace operators;

public static class BooleanLogicalOperators
{
    public static void Examples()
    {
        Console.WriteLine("==== !, &, |, ^ operators");
        Negation();
        And();
        Or();
        Xor();
        WithNullableBoolean();

        Console.WriteLine("==== && and || operators");
        ConditionalAnd();
        ConditionalOr();

        Console.WriteLine("==== Compound assignment and precedence");
        CompoundAssignment();
        Precedence();
    }

    private static void Negation()
    {
        // <SnippetNegation>
        bool passed = false;
        Console.WriteLine(!passed);  // output: True
        Console.WriteLine(!true);    // output: False
        // </SnippetNegation>
    }

    private static void And()
    {
        // <SnippetAnd>
        bool SecondOperand()
        {
            Console.WriteLine("Second operand is evaluated.");
            return true;
        }

        bool a = false & SecondOperand();
        Console.WriteLine(a);
        // Output:
        // Second operand is evaluated.
        // False

        bool b = true & SecondOperand();
        Console.WriteLine(b);
        // Output:
        // Second operand is evaluated.
        // True
        // </SnippetAnd>
    }

    private static void Or()
    {
        // <SnippetOr>
        bool SecondOperand()
        {
            Console.WriteLine("Second operand is evaluated.");
            return true;
        }

        bool a = true | SecondOperand();
        Console.WriteLine(a);
        // Output:
        // Second operand is evaluated.
        // True

        bool b = false | SecondOperand();
        Console.WriteLine(b);
        // Output:
        // Second operand is evaluated.
        // True
        // </SnippetOr>
    }

    private static void Xor()
    {
        // <SnippetXor>
        Console.WriteLine(true ^ true);    // output: False
        Console.WriteLine(true ^ false);   // output: True
        Console.WriteLine(false ^ true);   // output: True
        Console.WriteLine(false ^ false);  // output: False
        // </SnippetXor>
    }

    private static void ConditionalAnd()
    {
        // <SnippetConditionalAnd>
        bool SecondOperand()
        {
            Console.WriteLine("Second operand is evaluated.");
            return true;
        }

        bool a = false && SecondOperand();
        Console.WriteLine(a);
        // Output:
        // False

        bool b = true && SecondOperand();
        Console.WriteLine(b);
        // Output:
        // Second operand is evaluated.
        // True
        // </SnippetConditionalAnd>
    }

    private static void ConditionalOr()
    {
        // <SnippetConditionalOr>
        bool SecondOperand()
        {
            Console.WriteLine("Second operand is evaluated.");
            return true;
        }

        bool a = true || SecondOperand();
        Console.WriteLine(a);
        // Output:
        // True

        bool b = false || SecondOperand();
        Console.WriteLine(b);
        // Output:
        // Second operand is evaluated.
        // True
        // </SnippetConditionalOr>
    }

    private static void WithNullableBoolean()
    {
        // <SnippetWithNullableBoolean>
        bool? test = null;
        Display(!test);         // output: null
        Display(test ^ false);  // output: null
        Display(test ^ null);   // output: null
        Display(true ^ null);   // output: null

        void Display(bool? b) => Console.WriteLine(b is null ? "null" : b.Value.ToString());
        // </SnippetWithNullableBoolean>
    }

    private static void CompoundAssignment()
    {
        // <SnippetCompoundAssignment>
        bool test = true;
        test &= false;
        Console.WriteLine(test);  // output: False

        test |= true;
        Console.WriteLine(test);  // output: True

        test ^= false;
        Console.WriteLine(test);  // output: True
        // </SnippetCompoundAssignment>
    }

    private static void Precedence()
    {
        // <SnippetPrecedence>
        Console.WriteLine(true | true & false);   // output: True
        Console.WriteLine((true | true) & false); // output: False

        bool Operand(string name, bool value)
        {
            Console.WriteLine($"Operand {name} is evaluated.");
            return value;
        }

        var byDefaultPrecedence = Operand("A", true) || Operand("B", true) && Operand("C", false);
        Console.WriteLine(byDefaultPrecedence);
        // Output:
        // Operand A is evaluated.
        // True

        var changedOrder = (Operand("A", true) || Operand("B", true)) && Operand("C", false);
        Console.WriteLine(changedOrder);
        // Output:
        // Operand A is evaluated.
        // Operand C is evaluated.
        // False
        // </SnippetPrecedence>
    }
}