Question

Given: int num1, num2, newNum; double x, y; Which of the following assignments are valid? If an assignment is not valid, state the reason. When not given, assume that each variable is declared. a. num1 = 35; b. newNum = num1 – num2; c. num1 = 5; num2 = 2 + num1; num1 = num2 / 3; d. num1 * num2 = newNum; e. x = 12 * num1 - 15.3; f. num1 * 2 = newNum + num2; g. x / y = x * y; h. num2 = num1 % 2.0; i. newNum = static_cast (x) % 5; j. x = x + y - 5; k. newNum = num1 + static_cast (4.6 / 2);

Short answer

Valid assignments are: a, b, c, e, i, j, k. Invalid are: d, f, g, h.

Step-by-step solution

Variable Type Assignment

The first thing we need to examine is whether the left-hand side variable can accept the type of the right-hand side expression, considering both arithmetic and type consistency. For integers such as `num1` and `num2`, and doubles such as `x` and `y`, we need to ensure type compatibility.

Assignment 'a' Validity: num1 = 35;

Since `num1` is an integer and 35 is an integer, this assignment is valid.

Assignment 'b' Validity: newNum = num1 - num2;

`newNum` is an integer, and the subtraction of two integers (`num1` and `num2`) results in an integer. Therefore, this assignment is valid.

Assignment 'c' Validity: num1 = 5; num2 = 2 + num1; num1 = num2 / 3;

Each part is valid: `num1` is assigned an integer, `num2` is a sum of integers, and `num1 = num2 / 3` will conduct integer division, resulting in an integer as `num1` is an integer.

Assignment 'd' Validity: num1 * num2 = newNum;

This is invalid because the left-hand side is an expression (num1 * num2) which cannot be assigned a value.

Assignment 'e' Validity: x = 12 * num1 - 15.3;

`x` is a double and the right side of the equation results in a double after multiplying an integer and then subtracting a double. Thus, this assignment is valid.

Assignment 'f' Validity: num1 * 2 = newNum + num2;

This assignment is invalid because the left-hand side `num1 * 2` is an expression and cannot be assigned a value.

Assignment 'g' Validity: x / y = x * y;

This assignment is not valid since `x / y` is an expression rather than a variable that can store a value.

Assignment 'h' Validity: num2 = num1 % 2.0;

This assignment is invalid because the modulus operator `%` requires integer operands, and `2.0` is a double.

Assignment 'i' Validity: newNum = static_cast (x) % 5;

The `static_cast(x)` converts `x` to an integer, making this expression valid as it will use integer operands with the modulus operator `%`.

Assignment 'j' Validity: x = x + y - 5;

`x` is a double and the right side involves only arithmetic operations between doubles and an integer, resulting in a double, rendering this assignment valid.

Assignment 'k' Validity: newNum = num1 + static_cast (4.6 / 2);

The division results in a double which is converted to an integer. Adding `num1`, an integer, makes the full expression valid for assignment to `newNum`, an integer.

Key concepts

C++ Data Types

When programming in C++, understanding data types is crucial. Data types define the kind of data that variables can hold and the operations allowed on them. C++ offers several basic data types such as:

• int: Represents integer numbers without any decimal point. Utilized for operations that require whole numbers.
• double: Used for floating-point numbers, accommodating fractions and decimals. Suitable for more precise computations.

Assigning values in C++ requires consideration of these data types. For instance, assigning an integer value to an int variable is straightforward, while mixing types, like assigning a floating-point number to an integer variable without conversion, can lead to data loss.

Type Casting in C++

In some scenarios, you will need to convert a variable from one data type to another. This is known as type casting. Type casting in C++ can be done implicitly or explicitly:

• Implicit Casting: The compiler automatically converts types when needed. This often happens in expressions where variables are involved in arithmetic that require conversion to perform correctly.
• Explicit Casting: You, as the programmer, dictate the conversion using specific syntax. For instance, static_cast(x) explicitly converts the double x to an integer.

Using explicit casting helps control data conversion precisely, avoiding unexpected behavior such as data truncation or precision loss without your knowledge.

C++ Arithmetic Operations

Arithmetic operations in C++ involve performing calculations using different operators like addition, subtraction, multiplication, and division. Familiar arithmetic operators are "+" for addition, "-" for subtraction, "*" for multiplication, and "/" for division. Here are some details to keep in mind:

• Integer Arithmetic: When both operands in an operation are integers, C++ performs integer arithmetic, which means results are also integers. Division in integer arithmetic will truncate any decimal.
• Mixed Arithmetic: If the operands include both integers and doubles, the operation performs floating-point arithmetic yielding a double result. C++ automatically promotes integer operands to double in such cases.

Be cautious while using the modulus operator "%" as it only applies to integers and struggles with double types, potentially leading to errors.