Answer : Header files allow you to share common information among various source files.

For a function, we define the function declaration as the return type, the name of the function, and the list of arguments. The function definition is the function declaration followed by the function body. For example:

// function declaration double compute_root( double a, double b, double c );

// function definition double compute_root( double a, double b, double c ) { double delta = b * b - 4 * a * c;

if( delta < 0 ) { cout << "Error!" << endl; return 0.0; }

return ( - b + sqrt( delta ) ) / ( 2 * a ); }

Obviously, the declaration and the definition have to match for the same function!

Suppose you create some functions called A, B, and C and you put them in the same source file called myfuncs.C. Let's suppose that the function A needs to call another small function called A1. We can put A1 in myfuncs.C also.

In C++ (and C), the functions A, B, C, and A1 are only known only inside the file myfuncs.C. Inside that file, any function (A, B, C, or A1) can call any other function. If you write a main function and put it in a file main.C, it will not know about the functions A, B, C, or A1. If you try to call A (or B, or C, or A1) from main, you will get a compile-time error, because the compiler does not know about those functions when it reads the main.C file.

To fix this, we have to somehow have main.C know about the functions it uses. The easiest way to do this is to put the function definitions for the function used by main inside the main.C file. So we can do this for every file that uses the functions A, B, or C. This is one solution, but it is incomplete. What happens if we add one parameter to the arguments of the function A? Then we have to go and modify all the files that use the function A to know about the new parameter! This is cumbersome and prone to error.

We can just put the function declarations in a header file named myfuncs.h (so we know it contains declarations for functions in myfuncs.C) and

include myfuncs.h in each source file that uses those

functions. This way, we just need to modify the header file myfuncs.h and the source file myfuncs.C whenever we change the function arguments.

So header files (.h) help us share common information among source files (.C).

for functions: If functions A, B, and C, in file1.C are called from file2.C, create a header file named file1.h, put the declarations of A, B, and C in file1.h, and

include "file1.h" in file2.C.

for structures (struct, union, class): If the structure is used by functions in file1.C and file2.C, create a header file named common.h, put the definition of the structure in common.h, and

include "common.h" in both file1.C and

file2.C. for constants (const int, const double, ...): Similar to structures.

Obviously, the rules above can be extended to more than two files.

Keep in mind that these rules are not part of the language, the compiler does not enforce them, but they are standard programming practice.

The error message "Function definitions are not permitted in this context" suggests that you are trying to define a function within a script or another function. In MATLAB, function definitions should be placed in separate files with the same name as the function. The error message "Function definitions are not permitted in this context" suggests that you are trying to define a function within a script or another function. In MATLAB, function definitions should be placed in separate files with the same name as the function.

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Final Answer

Video Answer

Solved by verified expert

![Problem: My Matlab code reads an error message for the following problem. My Code: function fact = fact2(x) if(isscalar(x) && x = 0)

a = 1;
k = 1;
while(k  x)
    k = k + 1;
    a = a * k;
end
fprintf("a = %d", a);
fact = a;

else

fprintf("input must be a positive integer");

end end Error Message: function fact = fact2(x) | Error: Function definitions are not permitted in this context. CALCULATING FACTORIALS WITH A WHILE LOOP Create a new function called fact2 that uses a while loop to find M. Include an if statement to check for negative numbers and to confirm that the input is a scalar. Check to see if it is a scalar Not a scalar Initialize a to 1 and k to 1 Positive integer while k x

You've run out of values in the index matrix
k = k + 1
a = a * k

Output to the main program End Figure 9.7 Flowchart for finding the factorial with a while loop](https://https://i0.wp.com/cdn.numerade.com/project-universal/previews/3a075a3b-3988-4362-a760-f099e51868fd_large.jpg)

Solved on Feb. 18, 2023, 3:06 p.m.

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Shiksha O Anusandhan University, Bhubaneswar I am a student and persuing my graduation from ITER, SOA University, Bhubaneswar, Orrisa, India. Chemistry and Physics are my field of interest and love teaching both the subjects.