What does "&&" do?

Question

I can't seem to find the resource I need. What does && do in a code that is comparing variables to determine if they are true? If there is a link with a list of the symbol comparisons that would be greatly appreciated. example: Expresssion 1: r = !z && (x % 2);

Answer 1

In most programming languages that use &&, it's the boolean "and" operator. For example, the pseudocode if (x && y) means "if x is true and y is true."

In the example you gave, it's not clear what language you're using, but

r = !z && (x % 2);

probably means this:

r = (not z) and (x mod 2)
  = (z is not true) and (x mod 2 is true)
  = (z is not true) and (x mod 2 is not zero)
  = (z is not true) and (x is odd)

Answer 2

In most programming languages, the operator && is the logical AND operator. It connects to boolean expressions and returns true only when both sides are true.

Here is an example:

int var1 = 0;
int var2 = 1;

if (var1 == 0 && var2 == 0) {
      // This won't get executed.
} else if (var1 == 0 && var2 == 1) {
      // This piece will, however.
}

Although var1 == 0 evaluates to true, var2 is not equals to 0. Therefore, because we are using the && operator, the program won't go inside the first block.

Another operator you will see ofter is || representing the OR. It will evaluate true if at least one of the two statements are true. In the code example from above, using the OR operator would look like this:

int var1 = 0;
int var2 = 1;

if (var1 == 0 || var2 == 0) {
      // This will get executed.
}

I hope you now understand what these do and how to use them!

PS: Some languages have the same functionality, but are using other keywords. Python, e.g. has the keyword and instead of &&.

Answer 3

It is the logical AND operator

(&&) returns the boolean value true if both operands are true and returns false otherwise.

boolean a=true;
boolean b=true;    
    if(a && b){
      System.out.println("Both are true"); // Both condition are satisfied
    }

Output

Both are true

Answer 4

The exact answer to your question depends on the which language your are coding in. In R, the & operator does the AND operation pairwise over two vectors, as in:

c(T,F,T,F) & c(T,T,F,F)
#>  TRUE FALSE FALSE FALSE

whereas the && operator operated only on the first element of each vector, as in:

c(T,F,T,F) && c(T,T,F,F)
#> TRUE 

The OR operators (| and ||) behave similarly. Different languages will have different meanings for these operators.

Answer 5

In C && works like a logical and, but it only operates on bool types which are true unless they are 0.

In contrast, & is a bitwise and, which returns the bits that are the same.

Ie. 1 && 2 and 1 && 3 are true.

But 1 & 2 is false and 1 & 3 is true.

Answer 6

Let's imagine the situation:

a = 1 b = 2

if a = 1 && b = 2 return "a is 1 and b is 2"

if a = 1 && b = 3 return "a is 1 and b is 3"

In this situation, because a equals 1 AND b = 2, the top if block would return true and "a is 1 and b is 2" would be printed. However, in the second if block, a = 1, but b does not equal 3, so because only one statement is true, the second result would not be printed. && Is the exact same as just saying and, "if a is 1 and b is 1".