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C Structure and Function In this article, you'll find relevant examples to pass structures as an argument to a function, and use them in your program. Structure variables can be passed to a function and returned in a similar way as normal arguments. Nov 29, 2016 You can get visibility into the health and performance of your Cisco ASA environment in a single dashboard. View VPN tunnel status and get help monitoring firewall high availability, health, and readiness. It’s also designed to automatically discover and filter with ACLs, show rule hit counts, and detect shadow and redundant rules.
The classic function notation looks like this: functionName. In the previous snippet we would be calling a function called functionName which doesn't take any values to work properly (if it took any values - we'd put them in the brackets). A classic example of a function is the sqrt function which is defined inside math.h. We used this back in the basic mathematics tutorial, it simply square roots any value you pass to it. The classic function notation looks like this: functionName. In the previous snippet we would be calling a function called functionName which doesn't take any values to work properly (if it took any values - we'd put them in the brackets). A classic example of a function is the sqrt function which is defined inside math.h. We used this back in the basic mathematics tutorial, it simply square roots any value you pass. The structure variable p is passed to getData function which takes input from user which is then returned to main function. P = getData(p); Note: The value of all members of a structure variable can be assigned to another structure using assignment operator = if both structure variables are of same type. Functions in c programming with examples: A function is a block of statements, which is used to perform a specific task. Types: predefined and user-defined. As this implies, function pointers must point to functions with the same data-type and parameter types (as well as number of parameters). The syntax, visually, looks like data-type (.pointerName)(parameters). The easiest way to get used to function pointers is to just keep using them.
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C++ does not allow to pass an entire array as an argument to a function. However, You can pass a pointer to an array by specifying the array's name without an index.
If you want to pass a single-dimension array as an argument in a function, you would have to declare function formal parameter in one of following three ways and all three declaration methods produce similar results because each tells the compiler that an integer pointer is going to be received.
Way-1
Formal parameters as a pointer as follows −
Way-2
Formal parameters as a sized array as follows −
Way-3
Formal parameters as an unsized array as follows −
Now, consider the following function, which will take an array as an argument along with another argument and based on the passed arguments, it will return average of the numbers passed through the array as follows −
Now, let us call the above function as follows −
When the above code is compiled together and executed, it produces the following result −
As you can see, the length of the array doesn't matter as far as the function is concerned because C++ performs no bounds checking for the formal parameters.
- C++ Basics
- C++ Object Oriented
- C++ Advanced
- C++ Useful Resources
- Selected Reading
A function is a group of statements that together perform a task. Every C++ program has at least one function, which is main(), and all the most trivial programs can define additional functions.
You can divide up your code into separate functions. How you divide up your code among different functions is up to you, but logically the division usually is such that each function performs a specific task.
A function declaration tells the compiler about a function's name, return type, and parameters. A function definition provides the actual body of the function.
The C++ standard library provides numerous built-in functions that your program can call. For example, function strcat() to concatenate two strings, function memcpy() to copy one memory location to another location and many more functions.
A function is known with various names like a method or a sub-routine or a procedure etc.
Defining a Function
The general form of a C++ function definition is as follows −
A C++ function definition consists of a function header and a function body. Here are all the parts of a function −
Return Type − A function may return a value. The return_type is the data type of the value the function returns. Some functions perform the desired operations without returning a value. In this case, the return_type is the keyword void.
Function Name − This is the actual name of the function. The function name and the parameter list together constitute the function signature.
Parameters − A parameter is like a placeholder. When a function is invoked, you pass a value to the parameter. This value is referred to as actual parameter or argument. The parameter list refers to the type, order, and number of the parameters of a function. Parameters are optional; that is, a function may contain no parameters.
Function Body − The function body contains a collection of statements that define what the function does.
Example
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Following is the source code for a function called max(). This function takes two parameters num1 and num2 and return the biggest of both −
Function Declarations
A function declaration tells the compiler about a function name and how to call the function. The actual body of the function can be defined separately.
A function declaration has the following parts −
For the above defined function max(), following is the function declaration −
Parameter names are not important in function declaration only their type is required, so following is also valid declaration −
Function declaration is required when you define a function in one source file and you call that function in another file. In such case, you should declare the function at the top of the file calling the function.
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Calling a Function
While creating a C++ function, you give a definition of what the function has to do. To use a function, you will have to call or invoke that function.
When a program calls a function, program control is transferred to the called function. A called function performs defined task and when it’s return statement is executed or when its function-ending closing brace is reached, it returns program control back to the main program.
To call a function, you simply need to pass the required parameters along with function name, and if function returns a value, then you can store returned value. For example −
I kept max() function along with main() function and compiled the source code. While running final executable, it would produce the following result −
Function Arguments
If a function is to use arguments, it must declare variables that accept the values of the arguments. These variables are called the formal parameters of the function.
The formal parameters behave like other local variables inside the function and are created upon entry into the function and destroyed upon exit.
While calling a function, there are two ways that arguments can be passed to a function −
| Sr.No | Call Type & Description |
|---|---|
| 1 | Call by Value This method copies the actual value of an argument into the formal parameter of the function. In this case, changes made to the parameter inside the function have no effect on the argument. |
| 2 | Call by Pointer This method copies the address of an argument into the formal parameter. Inside the function, the address is used to access the actual argument used in the call. This means that changes made to the parameter affect the argument. |
| 3 | Call by Reference This method copies the reference of an argument into the formal parameter. Inside the function, the reference is used to access the actual argument used in the call. This means that changes made to the parameter affect the argument. |
By default, C++ uses call by value to pass arguments. In general, this means that code within a function cannot alter the arguments used to call the function and above mentioned example while calling max() function used the same method.
Default Values for Parameters
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When you define a function, you can specify a default value for each of the last parameters. This value will be used if the corresponding argument is left blank when calling to the function.
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This is done by using the assignment operator and assigning values for the arguments in the function definition. If a value for that parameter is not passed when the function is called, the default given value is used, but if a value is specified, this default value is ignored and the passed value is used instead. Consider the following example −
When the above code is compiled and executed, it produces the following result −