Learning tutorials for logical operators and conditional operators in C language _c language

logical operators

A logical operator that combines an expression containing a relational operator to form a new expression; The result is either true or false, and the result value is stored with the BOOL type variable.

Operator	Explain	Combination method
() []->.	Parentheses (functions, etc.), array, two struct members access	From left to right
! ~ ++ -- + -  * & ( type ) sizeof	negation, bitwise negation, increment, decrement, plus sign, Indirect, take address, type conversion, find size	From right to left
* / %	Multiply, divide, take modulo	From left to right
+ -	Plus, minus	From left to right
<< >>	Move left, move right	From left to right
< <= >= >	Less than, less than equal, greater than or equal, greater than	From left to right
== !=	Equal to, not equal to	From left to right
&	Bitwise AND	From left to right
^	Per-bitwise XOR OR	From left to right
|	by bit or	From left to right
&&	Logic and	From left to right
||	Logical OR	From left to right
? :	Conditions	From right to left
= += -= *= /=  &= ^= |= <<= >>=	Various assignments	From right to left
,	Commas (order)	From left to right

How to use:

Expression 1 logical operator Expression 2

Logic and: a >= b && a > 5 The result of an expression is false if the expression is true when both sides of the operator are true, and when an expression is false.

int a = 5;
int b = 6;
if (a >= b && a > 5)
{
 printf (the expression is true \ n);
}
else 
{
 printf ("The expression is fake \ n");
}

int a = 5;
int b = 6;
if (a >= b && a > 5)
{
 printf (the expression is true \ n);
}
else 
{
 printf ("The expression is fake \ n");
}

You can try changing the values of A and B to see the results.

Logic or: a >= B | | A > 5 only one of the results is true, and this expression is true.

int a = 6;
int b = 7;
if (a >= B | | a > 5)
{
 printf ("True for Expression");
}
else
{
 printf ("The expression is fake \ n");
}

int a = 6;
int b = 7;
if (a >= B | | a > 5)
{
 printf ("True for Expression");
}
else
{
 printf ("The expression is fake \ n");
}

A >= B is false, but a > 5 is true, so it prints: the expression is true.

Logical Non:! A, if a is true, then!a is false, if a is false, then!a is true.

BOOL flag = YES;
printf ("!flag =%d\n",!flag);
printf ("flag =%d\n", flag);

BOOL flag = YES;
printf ("!flag =%d\n",!flag);
printf ("flag =%d\n", flag);

First line printout:!flag = 0

Second line printout: flag = 1

Short-circuit of logical operators

Logic and short circuit:&& left is false, the right does not participate in the operation.

For example:

int a = 6;
int b = 0;
if (a >= && b = 5)
{
 printf ("The value of the expression is true \ n");
}
printf ("B =%d\n", b);

int a = 6;
int b = 0;
if (a >= && b = 5)
{
 printf ("The value of the expression is true \ n");
}
printf ("B =%d\n", b);

The output of B here is: 0, because in expression a >= && B = 5, a >= 6 is true, so the right side B = 5 does not participate in the operation, so B is equal to the original 0.

Short Circuit of logic or: | | The left is true and the right-hand side does not participate in the operation.

For example:

int a = 6;
int b = 0;
if (a >= 6 | | b = 5)
{
 printf ("The value of the expression is true \ n");
}
printf ("B =%d\n", b);

int a = 6;
int b = 0;
if (a >= 6 | | b = 5)
{
 printf ("The value of the expression is true \ n");
}
printf ("B =%d\n", b);

The output of B here is: 0, because in expression a >= 6 | | b = 5, a >= 6 is true, so B = 5 on the right side does not participate in the operation, so B is equal to the original 0.

Conditional operator

The symbol is this?: A question mark and a colon, an English character. The only three-mesh operator in the C language.

The general form of a conditional expression consisting of a conditional operator is:

Conditional expression? Expression 1: Expression 2

If the conditional expression is true, the value of the entire expression is the value of expression 1;

If the conditional expression is false, the value of the entire expression is the value of expression 2.

Find the maximum of three numbers, which is written using the conditional operator:

int a = 5;
int b = 6;
int c = 9;
int max = a > B? A:B;
max = max > c? Max:c;
It can also be written, simpler
//int max = a > B? (A > C. a:c): (b > C. b:c);

int a = 5;
int b = 6;
int c = 9;
int max = a > B? A:B;
max = max > c? Max:c;
It can also be written, simpler
//int max = a > B? (A > C. a:c): (b > C. b:c);