chap4.lst

Csharp2完全参考手册源代码 详细的说明可以在书里看到 该书是08年刚出炉很新鲜

listing 1
// Demonstrate the % operator. 
 
using System; 
 
class ModDemo {    
  public static void Main() {    
    int iresult, irem; 
    double dresult, drem; 
 
    iresult = 10 / 3; 
    irem = 10 % 3; 
 
    dresult = 10.0 / 3.0; 
    drem = 10.0 % 3.0;  
 
    Console.WriteLine("Result and remainder of 10 / 3: " + 
                       iresult + " " + irem); 
    Console.WriteLine("Result and remainder of 10.0 / 3.0: " + 
                       dresult + " " + drem); 
  }    
}

listing 2
/* 
   Demonstrate the difference between prefix 
   postfix forms of ++. 
*/ 
using System; 
 
class PrePostDemo {  
  public static void Main() {    
    int x, y; 
    int i; 
 
    x = 1; 
    Console.WriteLine("Series generated using y = x + x++;"); 
    for(i = 0; i < 10; i++) { 
 
      y = x + x++; // postfix ++ 
 
      Console.WriteLine(y + " "); 
    } 
    Console.WriteLine(); 
 
    x = 1; 
    Console.WriteLine("Series generated using y = x + ++x;"); 
    for(i = 0; i < 10; i++) { 
 
      y = x + ++x; // prefix ++ 
 
      Console.WriteLine(y + " "); 
    } 
    Console.WriteLine(); 
    
  } 
}

listing 3
// Demonstrate the relational and logical operators. 
 
using System; 
 
class RelLogOps {    
  public static void Main() {    
    int i, j; 
    bool b1, b2; 
 
    i = 10; 
    j = 11; 
    if(i < j) Console.WriteLine("i < j"); 
    if(i <= j) Console.WriteLine("i <= j"); 
    if(i != j) Console.WriteLine("i != j"); 
    if(i == j) Console.WriteLine("this won't execute"); 
    if(i >= j) Console.WriteLine("this won't execute"); 
    if(i > j) Console.WriteLine("this won't execute"); 
 
    b1 = true; 
    b2 = false; 
    if(b1 & b2) Console.WriteLine("this won't execute"); 
    if(!(b1 & b2)) Console.WriteLine("!(b1 & b2) is true"); 
    if(b1 | b2) Console.WriteLine("b1 | b2 is true"); 
    if(b1 ^ b2) Console.WriteLine("b1 ^ b2 is true"); 
  }    
}

listing 4
// Create an implication operator in C#. 
 
using System; 
 
class Implication {  
  public static void Main() {    
    bool p=false, q=false; 
    int i, j; 
 
    for(i = 0; i < 2; i++) { 
      for(j = 0; j < 2; j++) { 
        if(i==0) p = true; 
        if(i==1) p = false; 
        if(j==0) q = true; 
        if(j==1) q = false; 
         
        Console.WriteLine("p is " + p + ", q is " + q); 
        if(!p | q) Console.WriteLine(p + " implies " + q + 
                    " is " + true);   
        Console.WriteLine(); 
      } 
    } 
  } 
}

listing 5
// Demonstrate the short-circuit operators. 
 
using System; 
 
class SCops {    
  public static void Main() {    
    int n, d; 
 
    n = 10; 
    d = 2; 
    if(d != 0 && (n % d) == 0) 
      Console.WriteLine(d + " is a factor of " + n); 
 
    d = 0; // now, set d to zero 
 
    // Since d is zero, the second operand is not evaluated. 
    if(d != 0 && (n % d) == 0) 
      Console.WriteLine(d + " is a factor of " + n);  
     
    /* Now, try the same thing without short-circuit operator. 
       This will cause a divide-by-zero error.  */ 
    if(d != 0 & (n % d) == 0) 
      Console.WriteLine(d + " is a factor of " + n); 
  }    
}

listing 6
// Side-effects can be important. 
 
using System; 
 
class SideEffects {    
  public static void Main() {    
    int i; 
    bool someCondition = false; 
 
    i = 0; 
 
    /* Here, i is still incremented even though 
       the if statement fails. */ 
    if(someCondition & (++i < 100)) 
       Console.WriteLine("this won't be displayed"); 
    Console.WriteLine("if statement executed: " + i); // displays 1 
 
    /* In this case, i is not incremented because 
       the short-circuit operator skips the increment. */ 
    if(someCondition && (++i < 100)) 
      Console.WriteLine("this won't be displayed"); 
    Console.WriteLine("if statement executed: " + i); // still 1 !! 
  }    
}

listing 7
// Use bitwise AND to make a number even. 
 
using System; 
 
class MakeEven {  
  public static void Main() { 
    ushort num;  
    ushort i;     
 
    for(i = 1; i <= 10; i++) { 
      num = i; 
 
      Console.WriteLine("num: " + num); 
 
      num = (ushort) (num & 0xFFFE); // num & 1111 1110 
 
      Console.WriteLine("num after turning off bit zero: " 
                        +  num + "\n");  
    } 
  } 
}

listing 8
//  Use bitwise AND to determine if a number is odd. 
 
using System; 
 
class IsOdd {  
  public static void Main() { 
    ushort num;  
 
    num = 10; 
 
    if((num & 1) == 1) 
      Console.WriteLine("This won't display."); 
 
    num = 11; 
 
    if((num & 1) == 1) 
      Console.WriteLine(num + " is odd."); 
 
  } 
}

listing 9
// Display the bits within a byte.  
 
using System; 
 
class ShowBits { 
  public static void Main() { 
    int t; 
    byte val;  
  
    val = 123; 
    for(t=128; t > 0; t = t/2) { 
      if((val & t) != 0) Console.Write("1 ");  
      if((val & t) == 0) Console.Write("0 ");  
    } 
  } 
}

listing 10
//  Use bitwise OR to make a number odd. 
 
using System; 
 
class MakeOdd {  
  public static void Main() { 
    ushort num;  
    ushort i;     
 
    for(i = 1; i <= 10; i++) { 
      num = i; 
 
      Console.WriteLine("num: " + num); 
 
      num = (ushort) (num | 1); // num | 0000 0001 
 
      Console.WriteLine("num after turning on bit zero: " 
                        +  num + "\n");  
    } 
  } 
}

listing 11
// Use XOR to encode and decode a message. 
 
using System; 
 
class Encode {  
  public static void Main() { 
    char ch1 = 'H'; 
    char ch2 = 'i'; 
    char ch3 = '!'; 
    int key = 88; 
 
    Console.WriteLine("Original message: " + ch1 + ch2 + ch3); 
 
    // encode the message 
    ch1 = (char) (ch1 ^ key); 
    ch2 = (char) (ch2 ^ key); 
    ch3 = (char) (ch3 ^ key); 
 
    Console.WriteLine("Encoded message: " + ch1 + ch2 + ch3); 
 
    // decode the message 
    ch1 = (char) (ch1 ^ key); 
    ch2 = (char) (ch2 ^ key); 
    ch3 = (char) (ch3 ^ key); 
    
    Console.WriteLine("Encoded message: " + ch1 + ch2 + ch3); 
  } 
}

listing 12
// Demonstrate the bitwise NOT. 
 
using System; 
 
class NotDemo { 
  public static void Main() { 
    sbyte b = -34; 
 
    for(int t=128; t > 0; t = t/2) { 
      if((b & t) != 0) Console.Write("1 ");  
      if((b & t) == 0) Console.Write("0 ");  
    } 
    Console.WriteLine(); 
 
    // reverse all bits 
    b = (sbyte) ~b; 
 
    for(int t=128; t > 0; t = t/2) { 
      if((b & t) != 0) Console.Write("1 ");  
      if((b & t) == 0) Console.Write("0 ");  
    } 
  } 
}

listing 13
// Demonstrate the shift << and >> operators. 
 
using System; 
 
class ShiftDemo { 
  public static void Main() { 
    int val = 1; 
 
    for(int i = 0; i < 8; i++) {  
      for(int t=128; t > 0; t = t/2) { 
        if((val & t) != 0) Console.Write("1 ");  
        if((val & t) == 0) Console.Write("0 ");  
      } 
      Console.WriteLine(); 
      val = val << 1; // left shift 
    } 
    Console.WriteLine(); 
 
    val = 128; 
    for(int i = 0; i < 8; i++) {  
      for(int t=128; t > 0; t = t/2) { 
        if((val & t) != 0) Console.Write("1 ");  
        if((val & t) == 0) Console.Write("0 ");  
      } 
      Console.WriteLine(); 
      val = val >> 1; // right shift 
    } 
  } 
}

listing 14
// Use the shift operators to multiply and divide by 2. 
 
using System; 
 
class MultDiv {  
  public static void Main() { 
    int n; 
 
    n = 10; 
 
    Console.WriteLine("Value of n: " + n); 
 
    // multiply by 2 
    n = n << 1; 
    Console.WriteLine("Value of n after n = n * 2: " + n); 
 
    // multiply by 4 
    n = n << 2; 
    Console.WriteLine("Value of n after n = n * 4: " + n); 
 
    // divide by 2 
    n = n >> 1; 
    Console.WriteLine("Value of n after n = n / 2: " + n); 
 
    // divide by 4 
    n = n >> 2; 
    Console.WriteLine("Value of n after n = n / 4: " + n); 
    Console.WriteLine(); 
 
    // reset n 
    n = 10; 
    Console.WriteLine("Value of n: " + n); 
 
    // multiply by 2, 30 times 
    n = n << 30; // data is lost 
    Console.WriteLine("Value of n after left-shifting 30 places: " + n); 
 
  } 
}

listing 15
// Prevent a division by zero using the ?. 
 
using System; 
 
class NoZeroDiv { 
  public static void Main() { 
    int result; 
 
    for(int i = -5; i < 6; i++) { 
      result = i != 0 ? 100 / i : 0; 
      if(i != 0)  
        Console.WriteLine("100 / " + i + " is " + result); 
    } 
  } 
}

listing 16
// Prevent a division by zero using the ?. 
 
using System; 
 
class NoZeroDiv2 { 
  public static void Main() { 
 
    for(int i = -5; i < 6; i++)  
      if(i != 0 ? true : false)  
        Console.WriteLine("100 / " + i + 
                           " is " + 100 / i); 
  } 
}