в 15:31, 26 мая 2010

2010-05-26T15:31:53Z

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2010-05-26T12:17:27Z

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==Side-effects of short-circuit operators==

<source lang="csharp">using System;

class Example {
public static void Main() {
int i;
bool someCondition = false;

i = 0;

Console.WriteLine("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

Console.WriteLine("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 !!
}
}</source>
<pre class=codeResult>i is still incremented even though the if statement fails.
if statement executed: 1
i is not incremented because the short-circuit operator skips the increment.
if statement executed: 1</pre>

==The short-circuit operators==

The short-circuit AND operator is && and the short-circuit OR operator is ||.
As described earlier, their normal counterparts are & and |.
The normal operands will always evaluate each operand, but short-circuit versions will evaluate the second operand only when necessary.

<source lang="csharp">using System;

class Example {
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

Console.WriteLine("Since d is zero, the second operand is not evaluated.");
if(d != 0 && (n % d) == 0)
Console.WriteLine(d + " is a factor of " + n);

Console.WriteLine("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);
}
}</source>
<pre class=codeResult>2 is a factor of 10
Since d is zero, the second operand is not evaluated.
try the same thing without short-circuit operator. This will cause a divide-by-zero error.
Unhandled Exception: System.DivideByZeroException: Attempted to divide by zero.
at Example.Main()</pre>

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