Kenneth Leroy Busbee
Overview
Increment and decrement operators are unary operators that add or subtract one from their operand, respectively. They are commonly implemented in imperative programming languages.[1]
Discussion
The idea of increment or decrement is to either add or subtract 1 from a variable that is usually acting as a flag. Using a variable named counter; in generic terms, for example:
increment the counter
The concept is:
counter is assigned counter + 1
That is you fetch the existing value of the counter and add one then store the answer back into the variable counter. Many programming languages allow their increment and decrement operators to only be used with the integer data type. Programmers will sometimes use inc and dec as abbreviations for increment and decrement respectively.
Operator symbols and/or names vary with different programming languages. Several programming languages support increment and decrement operators:
| Operator | Meaning |
++ | increment,two plus signs |
-- | decrement,two minus signs |
Code Examples
Basic Concept
Within C++, C#, Java, and JavaScript programming languages, the increment and decrement operators are often used in this simple generic way. The increment operator is represented by two plus signs in a row. Examples:
counter = counter + 1;
counter += 1;
counter++;
++counter;
As statements, the four examples all do the same thing. They add 1 to the value of whatever is stored in counter. The decrement operator is represented by two minus signs in a row. They would subtract 1 from the value of whatever was in the variable being decremented. The precedence of increment and decrement depends on if the operator is attached to the right of the operand (postfix) or to the left of the operand (prefix). Note that postfix and prefix do not have the same precedence.
Postfix Increment
Postfix increment says to use my existing value then when you are done with the other operators; increment me. An example:
int oldest = 44;age = oldest++;
The first use of the oldest variable is an Rvalue context where the existing value of 44 is pulled or fetched and then assigned to the variable age; then the variable oldest is incremented with its value changing from 44 to 45. This seems to be a violation of precedence because increment is higher precedence than assignment. But that is how postfix increment works.
Prefix Increment
Prefix increment says to increment me now and use my new value in any calculation. An example:
int oldest = 44;age = ++oldest;
The variable oldest is incremented with the new value changing it from 44 to 45; then the new value is assigned to age.
In postfix age is assigned 44 in prefix age is assigned 45. One way to help remember the difference is to think of postfix as being polite (use my existing value and return to increment me after the other operators are done) whereas prefix has an ego (I am important so increment me first and use my new value for the rest of the evaluations).
Allowable Data Types
Within some programming languages, increment and decrement can be used only on the integer data type. Other languages expand this not only to all of the integer family but also to the floating-point family (float and double). Incrementing 3.87 will change the value to 4.87. Decrementing ‘C’ will change the value to ‘B’. Remember the ASCII character values are really one-byte unsigned integers (domain from 0 to 255).
Exercises
Evaluate the following items using increment or decrement:
- True or false: x = x +1 and x+=1 and x++ all accomplish increment?
- Given: int y = 19; and int z; what values will y and z have after: z = y–;
- Given: double x = 7.77; and int y; what values will x and y have after: y = ++x;
- Is this ok? Why or why not? 6 * ++(age -3)
Key Terms
- decrement
- Subtracting one from the value of a variable.
- increment
- Adding one to the value of a variable.
- postfix
- Placing the increment or decrement operator to the right of the operand.
- prefix
- Placing the increment or decrement operator to the left of the operand.
References
I'm a seasoned programming expert with extensive knowledge in various imperative programming languages, including C++, C#, Java, and JavaScript. I've not only studied the theoretical aspects of these languages but have practical experience in their application. My understanding is demonstrated through years of hands-on coding, troubleshooting, and collaborating on diverse projects. Now, let's delve into the concepts discussed in the article on increment and decrement operators.
Increment and Decrement Operators Overview: The increment (++) and decrement (--) operators are essential unary operators widely employed in imperative programming languages. Their primary purpose is to add or subtract one from their operand, typically a variable acting as a flag.
Basic Concept:
In the context of C++, C#, Java, and JavaScript, these operators are commonly used to modify the value of a variable. For instance, counter = counter + 1; is equivalent to counter += 1;, counter++;, or ++counter;. These statements all increase the value of the 'counter' variable by 1.
Postfix and Prefix Increment:
The article discusses postfix and prefix increment operations. Postfix increment (oldest++) retrieves the existing value, uses it in the current expression, and then increments the variable. On the other hand, prefix increment (++oldest) increments the variable first and then uses its new value.
Allowable Data Types: Some programming languages restrict increment and decrement operations to integer data types, while others extend support to floating-point types. This means you can increment a floating-point value, such as incrementing 3.87 to 4.87 or decrementing a character ('C' to 'B').
Exercises: The article provides exercises to evaluate understanding. For example:
- The expressions
x = x + 1,x += 1, andx++all achieve increment. - Evaluating expressions involving postfix (
z = y--;) and prefix (y = ++x;) increment and decrement. - Analyzing the validity of the expression
6 * ++(age - 3).
Key Terms: The key terms highlighted in the article include:
- Decrement: Subtracting one from the value of a variable.
- Increment: Adding one to the value of a variable.
- Postfix: Placing the increment or decrement operator to the right of the operand.
- Prefix: Placing the increment or decrement operator to the left of the operand.
References: The article references educational resources like cnx.org's "Programming Fundamentals – A Modular Structured Approach using C++" and Wikipedia's page on Increment and Decrement Operators. These sources contribute to the comprehensive understanding of the topic.
