Question

Consider the following function heading: void tryMe(int x[], int size); and the declarations: int list[100]; int score[50]; double gpas[50]; Which of the following function calls is valid? a. tryMe(list, 100); b. tryMe(list, 75); c. tryMe(score, 100); d. tryMe(score, 49); e. tryMe(gpas, 50);

Short answer

Calls a, b, and d are valid.

Step-by-step solution

Understand the Function Parameters

The function `tryMe` takes two parameters: an integer array and an integer representing the size of that array. The first parameter `int x[]` implies it's expecting an integer array, and the second `int size` is an integer value representing the number of elements in the passed array.

Evaluate Possible Options

Assess each option to determine if the call matches the expected parameters of `tryMe`. The key is matching parameter types and appropriate sizes.

Option A Analysis

Option a: `tryMe(list, 100);` - `list` is declared as `int list[100];`, meaning it is an integer array with size 100. - The size matches the expected size, hence this call is valid.

Option B Analysis

Option b: `tryMe(list, 75);` - `list` is still an integer array which is valid. - The size passed is less than 100, which is acceptable for arrays in such parameter passing contexts, so this call is valid.

Option C Analysis

Option c: `tryMe(score, 100);` - `score` is declared as `int score[50];`, hence it is an integer array but intended to be only size 50. - Passing a size of 100, which exceeds its maximum size, makes this call invalid.

Option D Analysis

Option d: `tryMe(score, 49);` - `score` is an integer array. - Passing a size less than or equal to its maximum size is valid, making this call acceptable.

Option E Analysis

Option e: `tryMe(gpas, 50);` - Although 50 is the defined size, `gpas` is declared as `double`, not `int`, which causes a type mismatch in argument passing. - Thus, this call is invalid because the array type is incorrect.

Key concepts

C++ Arrays

In C++, arrays are a fundamental way to store multiple elements of the same data type. Arrays are used when you need a collection of items that you want to reference using a single variable.

• Arrays in C++ are declared by specifying the data type, followed by the array name and the number of elements in square brackets. For instance, int list[100]; creates an integer array named list with 100 elements.
• When you work with arrays in function parameters, they need to be passed by reference, which means the function can modify the actual values in the array. In C++, you usually pass arrays by specifying them in the parameter list with square brackets, like int x[].

Understanding how arrays work is crucial to passing them correctly as parameters in functions.

Type Mismatch

Type mismatch is an error that occurs when the type of a function parameter does not match the type of the argument provided during a function call.

• Every function in C++ expects its parameters to be of certain types, and if they do not match, a compilation error occurs unless the types are implicitly convertible.
• For example, as shown in the exercise, the call tryMe(gpas, 50); is invalid because gpas is a double array and doesn't match the expected int array type in tryMe.

Being aware of type mismatches helps prevent function call errors, ensuring that your program compiles and runs correctly.

Parameter Passing

Parameter passing involves providing values to a function's parameters when it is called. In C++, you can pass parameters by value or by reference.

• When passing arrays, C++ passes them by reference automatically, meaning the function works with the actual array data.
• The "size" parameter, here an int, allows functions to know how many elements they should handle, even if only a subset of the array is needed, as seen with the tryMe(list, 75); call.

Understanding parameter passing correctly ensures you can control and manipulate data effectively within your functions.

Function Call Validation

Function call validation involves checking that the arguments provided at call time meet the function's expected types and requirements.

• Each function call must provide arguments that match the function's parameter declaration both in type and, in some circumstances, in logical constraint, such as size requirements in an array.
• This concept ensures that, for the function tryMe, only integer arrays and valid sizes are provided as arguments, with calls like tryMe(list, 100); and tryMe(score, 49); being correct.

By ensuring function call validation, C++ programs are not only syntactically correct but also logically sound, preventing runtime errors and unexpected behaviors.