C Tutorial/Operator/Logic Operators
Содержание
Boolean Operator in C
Character Set Boolean Operator && and || or
&& Operator
- && operator: evaluate a Boolean expression from left to right.
- Both sides of the operator must evaluate to true before the entire expression becomes true.
|| Operator
- || operator: evaluate from left to right.
- If either side of the condition is true, the whole expression results in true.
Logical AND (&&) returns a true value if both relational expressions are true.
Logical OR (||) returns true if any of the expressions are true.
Negations(!) return complements of values of relational expressions.
R1 R2 R1 && R2 R1 || R2 ! R1 T T T T F T F F T F F T F T T F F F F T
- Logical operators AND, and OR have higher priority than assignment operators.
- Logical operators AND, and OR have lower priority than relational operators.
- Negation operators have the same priority as unary operators.
Logical operator
You can combine multiple relations or logical operations by logical operation.
The logical operators are negation (!), logical AND (&&), and logical OR (||),
#include<stdio.h>
main(){
int c1 = 1,c2 = 2,c3 = 3;
if((c1 < c2) && (c1<c3)){
printf("\n c1 is less than c2 and c3");
}
if (!(c1< c2)){
printf("\n c1 is greater than c2");
}
if ((c1 < c2)||(c1 < c3)){
printf("\n c1 is less than c2 or c3 or both");
}
}c1 is less than c2 and c3
c1 is less than c2 or c3 or both
Short circuiting
When evaluating logical expressions, C uses the technique of short circuiting.
C1 && C2 && C3 && C4Ternary operator
Ternary operators return values based on the outcomes of relational expressions.
The general form of the ternary operator is:
(expr 1) ? expr2 : expr3Testing letters with logic operator and (&&)
#include <stdio.h>
int main(void)
{
char letter =0;
printf("Enter an upper case letter:");
scanf(" %c", &letter);
if ((letter >= "A") && (letter <= "Z"))
{
letter += "a"-"A";
printf("You entered an uppercase %c.\n", letter);
}
else
printf("You did not enter an uppercase letter.\n");
return 0;
}Enter an upper case letter:R
You entered an uppercase r.
The || is the logical OR operator.
#include <stdio.h>
int main()
{
char c;
printf("Y/y?");
c=getchar();
if(c=="Y" || c=="y")
{
printf("Bye!\n");
}
else
{
printf("Okay!\n");
}
return(0);
}Y/y?1
Okay!
