The singe pipe "|" is the "bitwise" or and should only be used when you know what you're doing. The double pipe "||" is a logical or, and can be used in logical statements, like "x == 0 || x == 1".
Here's an example of what the bitwise or does: if a=0101 and b=0011, then a|b=0111. If you're dealing with a logic system that treats any non-zero as true, then the bitwise or will act in the same way as the logical or, but it's counterpart (bitwise and, "&") will NOT. Also the bitwise or does not perform short circuit evaluation.
& - (Condition 1 & Condition 2): checks both cases even if first one is false
&& - (Condition 1 && Condition 2): dosen't bother to check second case if case one is false
&& - operator will make your code run faster, professionally & is rarely used
| - (Condition 1 | Condition 2): checks both cases even if case 1 is true
|| - (Condition 1 || Condition 2): dosen't bother to check second case if first one is true
|| - operator will make your code run faster, professionally | is rarely used
A single pipe (|) is the bitwise OR operator.
Two pipes (||) is the logical OR operator.
They are not interchangeable.
For bitwise | and Logicall ||
OR
bitwise & and logicall &&
it means if( a>b | a==0)
in this first left a>b will be evaluated and then a==0 will be evaluated then | operation will be done
but in|| if a>b then if wont check for next RHS
Similarly for & and &&
if(A>0 & B>0)
it will evalue LHS and then RHS then do bitwise & but
in(A>0 && B>0)
if(A>0) is false(LHS) it will directly return false;
Good question. These two operators work the same in PHP and C#.
| is a bitwise OR. It will compare two values by their bits. E.g. 1101 | 0010 = 1111. This is extremely useful when using bit options. E.g. Read = 01 (0X01) Write = 10 (0X02) Read-Write = 11 (0X03). One useful example would be opening files. A simple example would be:
File.Open(FileAccess.Read | FileAccess.Write); //Gives read/write access to the file
|| is a logical OR. This is the way most people think of OR and compares two values based on their truth. E.g. I am going to the store or I will go to the mall. This is the one used most often in code. For example:
if(Name == "Admin" || Name == "Developer") { //allow access } //checks if name equals Admin OR Name equals Developer
PHP Resource: http://us3.php.net/language.operators.bitwise
C# Resources: http://msdn.microsoft.com/en-us/library/kxszd0kx(VS.71).aspx
http://msdn.microsoft.com/en-us/library/6373h346(VS.71).aspx
|| is the logical OR operator. It sounds like you basically know what that is. It's used in conditional statements such as if, while, etc.
condition1 || condition2
Evaluates to true if either condition1 OR condition2 is true.
| is the bitwise OR operator. It's used to operate on two numbers. You look at each bit of each number individually and, if one of the bits is 1 in at least one of the numbers, then the resulting bit will be 1 also. Here are a few examples:
A = 01010101
B = 10101010
A | B = 11111111
A = 00000001
B = 00010000
A | B = 00010001
A = 10001011
B = 00101100
A | B = 10101111
Hopefully that makes sense.
So to answer the last two questions, I wouldn't say there are any caveats besides "know the difference between the two operators." They're not interchangeable because they do two completely different things.
The | operator performs a bitwise OR of its two operands (meaning both sides must evaluate to false for it to return false) while the || operator will only evaluate the second operator if it needs to.
http://msdn.microsoft.com/en-us/library/kxszd0kx(VS.71).aspx
http://msdn.microsoft.com/en-us/library/6373h346(VS.71).aspx
By their mathematical definition, OR and AND are binary operators; they verify the LHS and RHS conditions regardless, similarly to | and &.
|| and && alter the properties of the OR and AND operators by stopping them when the LHS condition isn't fulfilled.
Simple example in java
public class Driver {
static int x;
static int y;
public static void main(String[] args)
throws Exception {
System.out.println("using double pipe");
if(setX() || setY())
{System.out.println("x = "+x);
System.out.println("y = "+y);
}
System.out.println("using single pipe");
if(setX() | setY())
{System.out.println("x = "+x);
System.out.println("y = "+y);
}
}
static boolean setX(){
x=5;
return true;
}
static boolean setY(){
y=5;
return true;
}
}
output :
using double pipe
x = 5
y = 0
using single pipe
x = 5
y = 5
One is a "bitwise or".
10011b | 01000b => 11011b
The other is a logic or.
true or false => true
The single pipe, |, is one of the bitwise operators.
From Wikipedia:
In the C programming language family, the bitwise OR operator is "|" (pipe). Again, this operator must not be confused with its Boolean "logical or" counterpart, which treats its operands as Boolean values, and is written "||" (two pipes).
Source: Stackoverflow.com