Question

Consider the following statements: int num1, num2, num3; double length, width, height; double volume; num1 = 6; num2 = 7; num3 = 4; length = 6.2; width = 2.3; height = 3.4 and the function prototype: double box(double, double, double); Which of the following statements are valid? If they are invalid, explain why. a. volume = box(length, width, height); b. volume = box(length, 3.8, height); c. cout << box(num1, num3, num2) << endl; d. cout << box(length, width, 7.0) << endl; e. volume = box(length, num1, height); f. cout << box(6.2, , height) << endl; g. volume = box(length + width, height); h. volume = box(num1, num2 + num3);

Short answer

Valid: a, b, c, d, e. Invalid: f, g, h (wrong number of arguments).

Step-by-step solution

Validate Data Compatibility

Based on the function prototype given, `double box(double, double, double);`, the box function expects three arguments, each of type `double`. We have to ensure that each function call matches this prototype.

Evaluate Statement a

`volume = box(length, width, height);` is valid. All the variables `length`, `width`, and `height` are of type `double`, which matches the function's expected argument types.

Evaluate Statement b

`volume = box(length, 3.8, height);` is valid. The literal `3.8` is a `double`, and both `length` and `height` are `double` types. All three arguments are compatible with the expected types.

Evaluate Statement c

`cout << box(num1, num3, num2) << endl;` is valid but requires type implicit conversion. The variables `num1`, `num3`, and `num2` are integers, but they can be automatically converted to `double` for the function call.

Evaluate Statement d

`cout << box(length, width, 7.0) << endl;` is valid. The literal `7.0` is a `double`, and the other two variables `length` and `width` are `double` types, fitting the function's parameters.

Evaluate Statement e

`volume = box(length, num1, height);` is valid with an implicit conversion. `num1` is an `int`, but it can be automatically converted to `double`, fitting the function call requirements.

Evaluate Statement f

`cout << box(6.2, , height) << endl;` is invalid. The call is missing a second argument, making it incompatible with the function prototype that requires three arguments.

Evaluate Statement g

`volume = box(length + width, height);` is invalid because it only supplies two arguments. The function expects three `double` arguments.

Evaluate Statement h

`volume = box(num1, num2 + num3);` is invalid because it only provides two arguments to the function expecting three. `num2 + num3` will be implicitly converted to `double`, but still only forms one argument.

Key concepts

Implicit Type Conversion

In C++, implicit type conversion happens when data types are automatically converted by the compiler to match the required type. It's often referred to as "type coercion". This feature is quite helpful when you want your program to handle different data types seamlessly during operations or function calls.

For example, consider a function that expects arguments of type `double`. If you provide `int` variables instead, the compiler will automatically convert these integers into `double` values. This ensures compatibility between the types without requiring manual intervention.

In the given exercise, statements like `cout << box(num1, num3, num2) << endl;` leverage implicit type conversion. Although `num1`, `num2`, and `num3` are integers, they are automatically coerced into `double` types, aligning perfectly with the function's parameter expectations.

Function Prototype

A function prototype in C++ is a declaration of a function that informs the compiler about the function's name, return type, and parameters, without specifying the function's body. It acts like a contract, ensuring that any function call aligns with the declared prototype.

For example, in the exercise, the function prototype provided is `double box(double, double, double);`. This declaration informs the compiler that any function call to `box` must have three `double` parameters and will return a `double` value.

Prototypes play a critical role in validating function calls. They allow the compiler to catch errors at compile-time if functions are not called with the appropriate number of arguments or with compatible types. This mechanism is essential in maintaining robustness and accuracy within C++ programs.

Data Types in C++

Data types in C++ define the kind of data a variable can hold. They instruct the compiler on how to allocate memory and process the variable's contents. C++ supports various basic data types, including `int`, `double`, `float`, `char`, etc.

In the example provided, the exercise uses `int` for integer values and `double` for decimal numbers. This distinction is crucial as each data type operates differently in terms of memory allocation and precision.

• `int`: Used for whole numbers, like `num1`, `num2`, and `num3`.
• `double`: Used for floating-point numbers, providing more precision than a `float`. Variables like `length`, `width`, and `height` are declared as `double`.

Understanding data types is vital for efficient memory use and ensuring calculations are precise and accurate.

Argument Compatibility

Argument compatibility refers to the alignment between the arguments passed in a function call and the parameters expected by that function. Compatibility is essential because mismatched types can lead to unexpected behaviors or compile-time errors.

In C++, argument compatibility primarily focuses on the type and number of arguments. When calling a function, the given arguments must match or be compatible with the declared parameter types in the function's prototype. If implicit conversion is possible, types can be adjusted automatically to fit.

For example, in `volume = box(length, width, height);`, the arguments `length`, `width`, and `height` are all `double` types, aligning perfectly with the `box` function's prototype. On the other hand, `cout << box(num1, num3);` would be invalid because it offers only two integers where three `double` arguments are required, regardless of type conversion capabilities.