Question

Find the error in each of the following program segments and explain how to correct it: a. float cube( float ); // function prototype double cube( float number ) // function definition { return number * number * number; } b. register auto int x = 7; c. int randomNumber = srand(); d. float y = 123.45678; int x; x = y; cout << static_cast < float > ( x ) << endl; e. double square( double number ) { double number; return number * number; } f.int sum( int n ) { if ( n == 0 ) return 0; else return n + sum( n ); }

Short answer

Correct return types, remove illegal keywords, fix function logic, handle type conversions, avoid redefinition, and ensure recursion termination.

Step-by-step solution

Analyze Code Segment (a)

In this segment, there's a mismatch between the function prototype and function definition. The prototype specifies the return type as `float`, while the definition specifies `double`. To correct this error, both should have the same return type. Changing `double` to `float` in the function definition will resolve the issue.

Analyze Code Segment (b)

For the code `register auto int x = 7;`, the `auto` keyword cannot be used with `register`, as `auto` is a storage class specifier that became obsolete since C++11. Simply remove `auto` to fix the error, resulting in `register int x = 7;`.

Analyze Code Segment (c)

The function `srand()` is used to seed the random number generator and does not return a value. The use of `srand()` as a function returning a value is incorrect. Thus, `int randomNumber = srand();` should be corrected to just call `srand(someValue);` without assigning it to a variable. You can initialize `randomNumber` with `rand()` instead.

Analyze Code Segment (d)

The statement `x = y;` causes implicit conversion from `float` to `int`, which can lead to precision loss, and `cout << static_cast < float > ( x ) << endl;` attempts to output `x` as a float. Although syntactically correct, the conversion results in precision loss, which should be acknowledged by the programmer depending on the context.

Analyze Code Segment (e)

The error is in redefining the variable `number` within the function scope, leading to a scoping error. Removing or renaming the second declaration of `number` within the function will solve this issue.

Analyze Code Segment (f)

The function `sum()` causes infinite recursion due to missing decrement in the `else` branch. To correct it, change the last line to `return n + sum(n - 1);`, which ensures the recursion eventually terminates.

Key concepts

Function Prototypes and Definitions

In C++ programming, function prototypes and definitions play a crucial role in ensuring your program runs correctly and efficiently. A function prototype is a declaration of a function that specifies its return type, name, and parameters but doesn't contain the function body. It's like a blueprint for the function. The function definition, however, includes the actual body of the function where the operations are performed.

For example:

• Prototype: `float cube(float);`
• Definition: `double cube(float number) { return number * number * number; }`

The key is to ensure that the return type, name, and parameters in the prototype and definition match exactly. In the provided exercise, there's a mismatch: the prototype returns a `float`, while the definition returns a `double`. Correcting this mismatch by aligning both to the same return type, such as `float`, resolves the error.

Storage Class Specifiers

Storage class specifiers in C++ define the scope, visibility, and lifetime of variables and functions within a program. The most commonly used storage class specifiers are `auto`, `register`, `static`, and `extern`.

`auto` is used to automatically deduce the type of the variable and is the default storage class for local variables. However, since C++11, explicit use of `auto` as a storage class specifier was deprecated.

In contrast, `register` suggests that the variable should be stored in a CPU register instead of RAM to provide faster access. You cannot combine `auto` with `register`, as seen in the faulty code segment `register auto int x = 7;`. The correct usage is to simply specify `register int x = 7;`, especially since `auto` is now more about type deduction rather than storage class.

Type Conversion Errors

Type conversion errors occur in C++ when a variable of one type is assigned to another type that might not be compatible, leading to data loss or unexpected behavior. Implicit conversions happen automatically and can result in precision loss without a warning.

In the exercise, the statement `x = y;` involves an implicit conversion from `float` to `int`. Since `float` values can contain decimals, converting them to `int` results in truncating the decimal part, losing its precision.

To mitigate unwanted type conversions, you can use explicit conversions, such as the `static_cast` operator, which makes the conversion intention clear in the code. It's essential for programmers to understand when data loss or changes might occur during conversion and make conscious decisions to handle these conversions.

Recursion

Recursion in programming occurs when a function calls itself as part of its execution. It is a powerful technique that can simplify code for problems that have a repetitive nature or can be broken down into smaller, similar problems.

A base case is fundamental in recursion to prevent infinite execution. Without it, the function would call itself indefinitely, potentially causing a stack overflow. In the given exercise, the function `sum()` lacks a proper decrement step in its recursion, leading to infinite calls when `n != 0`.

Correcting the function by modifying the `else` clause to `return n + sum(n - 1);` ensures a decrement in `n` with each recursive call, moving the function closer to the base case when `n` becomes zero, thereby terminating the recursion effectively.