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What if not?
nullius in verba/memento mori/omnes una manet nox/sub specie aeternitatis
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Eskişehir, 18 Nisan
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Haziran 2021 tarihinde katıldı
değilleme operatörü, negation operator. ( ! )Yazılım
To easily test if the value of a flag is FALSE, you can use the logical negation operator, !. In the expression
if ( ! isPrime )
the logical negation operator is used to test if the value of isPrime is FALSE (read this statement as “if not isPrime”). In general, an expression such as
! expression
negates the logical value of expression. So if expression is zero, the logical negation operator produces a 1. And if the result of the evaluation of expression is nonzero, the negation operator yields a 0.
The logical negation operator can be used to easily “flip” the value of a flag, such as in the expression
myMove = ! myMove;
As you might expect, this operator has the same precedence as the unary minus operator, which means that it has higher precedence than all binary arithmetic operators and all relational operators. So to test if the value of a variable x is not less than the value of a variable y, such as in
! ( x < y )
the parentheses are required to ensure proper evaluation of the expression. Of course, you could have equivalently expressed the previous expression as
x >= y
Trying to predict the ways that a program can fail or produce unwanted results and then taking preventive measures to account for such situations is a necessary part of producing good, reliable programs. Running a sufficient number of test cases against a program often points the finger to portions of the program that do not account for certain cases. But it goes further than that. It must become a matter of self-discipline while coding a program to always say “What would happen if ...” and to insert the necessary program statements to handle the situation properly.
When forming compound relational expressions, liberally use parentheses to aid readability of the expression and to avoid getting into trouble because of a mistaken assumption about the precedence of the operators in the expression.You can also use blank spaces to aid in the expression’s readability.An extra blank space around the && and || operators visually sets these operators apart from the expressions that are being joined by
these operators
The compound operators can be used to form extremely complex expressions in C. The C language grants the programmer ultimate flexibility in forming expressions.This flexibility is a capability that is often abused. Simpler expressions are almost always easier to read and debug