Overloading binary operators in c sharp
This article describes the syntax of the C programming language. The features described are compatible with. NET Framework and Mono. An identifier is overloading binary operators in c sharp name of an element in the code. There are certain standard naming conventions to follow when selecting names for elements. Keywords are predefined reserved words with special syntactic meaning.
The language has two types of keyword — contextual and reserved. The reserved keywords such as false or byte may only be used as keywords. The contextual keywords such as where or from overloading binary operators in c sharp only treated as keywords in certain situations.
This facilitates reuse of. NET code written in other languages. The underscore symbol separates overloading binary operators in c sharp in number values for readability purposes. Compiler will ignore it. Generally, it may be put only between digit characters. Variables are identifiers associated with values. They are declared by writing the variable's type and name, and are optionally initialized in the same statement. This reduces repetition, especially for types with multiple generic type-parametersand adheres more closely to the DRY principle.
When declaring a local variable overloading binary operators in c sharp a field with the const keyword overloading binary operators in c sharp a prefix the value must be given when it is declared. After that it is locked and cannot overloading binary operators in c sharp. They can either be declared in the context as a field or a local variable. Constants are implicitly static. The readonly keyword does a similar thing to fields. Like fields marked as const they cannot change once overloading binary operators in c sharp.
The difference is that you can choose to initialize them in a constructor. This only works on fields. Read-only fields can either be members of an instance or static class members. Class members and the body of a method are examples of what can live inside these braces in various contexts.
A C application consists of classes and their members. Classes and other types exist in namespaces but can also be nested inside other classes. Whether it is a console or a graphical interface application, the program must have an entry point of some sort. The entry point of the C application is the Main method. There can only be one, and it is a static method in a class. The method usually returns void and is passed command-line arguments as an array of strings.
A Overloading binary operators in c sharp method is also allowed to return an integer value if specified. The using statement loads a specific namespace from a referenced assembly. It is usually placed in the top overloading binary operators in c sharp header of a code file but it can be placed elsewhere if wanted, overloading binary operators in c sharp. The statement can also be used to define another name for an existing namespace or type.
This is sometimes useful when names are too long and less readable. The cast operator is not overloadable but you can write a conversion operator method which lives in the target class. Conversion methods can define two varieties of operators, implicit and explicit conversion operators. The implicit operator will cast without specifying with the cast operator and the explicit operator requires it to be used.
The as operator will attempt to do a silent cast to a given type. If it succeeds it will return the object as the new type, if it fails it will return a null reference. Meaning that if the content of variable ifNotNullValue is not null, that content will be returned, otherwise the content of variable otherwiseValue is returned.
The if statement is entered when the given condition is true. Single-line case statements do not require block braces although it is mostly preferred by convention.
The switch construct serves as a filter for different values. Each value leads to a "case". It is not allowed to fall through case sections and therefore the keyword break is typically used to end a case.
An unconditional return in a case section can also be used to end a case. See also how goto statement can be used to fall through from one case to the next. Many cases may lead to the same code though. The default case handles all the other cases not handled by the construct.
Iteration statements are statements that are repeatedly executed when a given condition is evaluated as true. The for loop consists of three parts: Any of them can be left out as they are optional. Is equivalent to this code represented with a while statement, except here the i variable is not local to the loop. The foreach statement is derived from the for statement and makes use of a certain pattern described in C 's language specification in order to obtain and use an enumerator of elements to iterate over.
Each item in the given collection will be returned and reachable in the context of the code block. When the block has been executed the next item will be returned until there are no items remaining. They simply represent the jump-instructions of an assembly language that controls the flow of a program. Labels are given points in code that can be jumped to by using the goto statement.
The goto statement can be used in switch statements to jump from one case to another or to fall through from one case to the next. The break statement breaks out of the closest loop or switch statement. Execution continues in the statement after the terminated statement, if any.
The continue statement discontinues the current iteration of the current control statement and begins the next iteration. The while loop in overloading binary operators in c sharp code above reads characters by calling GetCharskipping the statements in the body of the loop if the characters are spaces.
The base class library has a class called System. Exception from which all other exception classes are derived. An Exception -object contains all the information about a specific exception and also the inner exceptions that were caused. Programmers may define their own exceptions by deriving from the Exception class.
Exceptions are managed within try The statements within the try block are executed, and if any of them throws an exception, execution of the block is discontinued and the exception is handled by the catch block.
There may be multiple catch blocks, in which case the first block with an exception variable whose type matches the type of the thrown exception is executed. If no catch block matches the type of the thrown exception, the execution of the outer block or method containing the try The exception is propagated upwards through the call stack until a matching catch block is found within one of the currently active methods.
If the exception propagates all the way up to the top-most Main method without a matching catch block being found, the entire program is terminated and a textual description of the exception is written to the standard output stream. The statements within the finally block are always executed after the try and catch blocks, whether or not an exception was thrown.
Such blocks are useful for providing clean-up code. Either a catch block, a finally block, or both, must follow the try block. That means that every variable and constant gets a fixed type when it is being declared. There are two kinds of types: Instances of value types reside on the stack, i.
If you declare a variable for a value type the memory gets allocated directly. If the variable gets out of scope the object is destroyed with it.
Structures are more commonly known as structs. Structs are user-defined value types that are declared using the struct keyword. They are very similar to classes but are more suitable for lightweight types. Some important syntactical differences between a class and a struct are presented later in this article. String is not a struct and is not a primitive type.
Enumerated types enums are named values representing integer values. They can be assigned or initialized to the named values defined by the enumeration type. Addition and subtraction between variables of the same type is allowed without any specific cast but multiplication and division is overloading binary operators in c sharp more risky and requires an explicit cast.
Casts are also required for converting enum variables to and from integer types. However, the cast will not throw an exception if the value is not specified by the enum type definition. Variables created for overloading binary operators in c sharp types are typed managed references.
When the constructor is called, an object is created on the heap and a reference is assigned to the variable. When a variable of an object goes out of scope the reference is broken and when there are no references left the object gets marked as garbage. The garbage collector will then soon collect and destroy it.
C is a mature language and at this point there are some features that are forgotten, or not even discovered, by users of the language.
I've previously written about one of my favorite "obscure" features: When creating your own classes as you very often doyou have the ability to set how the different operators in C should work with the class. While you're not allowed to create new operators, you can overload most of the existing ones. If we wanted to add those two points to get point3we'd have to do something like this:.
Let's make it simpler by overloading the plus operator. Let's add this method to the class definition of Point:. We define a static method that will return a Pointbut instead of giving it a name as usual, we say it's an operator and then which operator it is.
The parameters are the two points that are to be added. We then return the new point. It's worth noting that it's only required for one overloading binary operators in c sharp the parameters to be the same type as the containing type; meaning, you can define an overload for the plus operator between a Point and a double for example:.
And we can add 2 to both X and Y by adding a double to point You can check out the comprehensive list in the docs. This makes it easier to check whether two points are in the same place. In addition it's also strongly recommended to override Equals and GetHashCode. These two operators and two methods all relate overloading binary operators in c sharp equality and how to determine whether two objects are to be considered equal.
By overriding all of them, we ensure that they all calculate equality the same way. As you can see, this is pretty much the same as before. We receive to points and return true if the X and Y values are equal. This also makes the! Now we can easily check whether to points are equal. Let's declare point5 which has the same X and Y values as point You can of course overload other equality operators too: You can overloading binary operators in c sharp more about this in the docs.
The last kind of operator I want to show how to overload, are the conversion operators. These are the operators used when you do implicit and explicit conversion from one type to another. For example, you can implicitly cast an int to a double by writing this:. While the 1 is an intthe double type knows how to create a double overloading binary operators in c sharp an int and can do so for you automatically. Going the other way, though, is not as automatic.
You have to specify that you want to overloading binary operators in c sharp the double to become an int by doing an explicit cast:. It's up to each type whether a conversion from another type should be implicit or explicit, but the rule of thumb is that implicit conversion should only be done when you can ensure no loss of information. Explicit conversion is for when you can say "you could do this, but The but indicates an explicit conversion.
Now let's have a look at how to implement this dandy feature in our Point class. To make it easy overloading binary operators in c sharp create a Point with the same X and Y value, we should be able to just provide a double and implicitly cast that to a Point:.
As you can see, it looks very much like the previous overloads. The difference is that the "return type" becomes implicit and the name of the method is the type that is returned after the conversion. It's a bit strange how they're switched around, but there you go.
This is actually a bit more clever than you might think: The 6 is actually an intbut our Point class only support conversion from a double. However, since int can be implicitly converted to a doublewhich is supported by PointC does the conversion automatically.
To demonstrate explicit conversion, we're going to provide a conversion from Point and back to double. When doing this conversion, the double is going to overloading binary operators in c sharp the length of the line between the Point and the origin, the 0,0 coordinate. We want this conversion to be explicit as there is a loss of information:.
By overloading conversion operators you're able to provide an easy way to convert between your custom class and any other class. While our Point class should probably been a structI purposely used a class to demonstrate the equality operator overloads. In structs these are handled differently: If they are all equal, the structs are considered equal. While our Point class does the same thing, I just wanted to show how it's done manually. Let's start with a simple class which represents a point in a two dimensional space: Especially if you are going to do this operation a lot.
Let's add this method to the class definition of Point: It's worth noting that it's only required for one of the parameters to be the same type as the containing type; meaning, you can define an overload for the plus operator between a Point and a double for example: We can now declare point3 more succinctly: Y; As you can see, this is pretty much the same as before.
Let's declare point5 which has the same X and Y values as point4: For example, you can implicitly cast an overloading binary operators in c sharp to a double by writing this: You have to specify that you overloading binary operators in c sharp to force the double to become an int by doing an explicit cast: To make it easy to create a Point with the same X and Y value, we should be able to just provide a double and implicitly cast that to a Point: This means that we can now do this: We want this conversion to be explicit as there is a loss of information: Y; public static bool operator!
Going back as far as the punched card, computer scientists have concerned themselves with the mathematical nature of their work. Programming languages have long provided addition, subtraction, multiplication, division and equality checks for the primitive data types like INT, FLOAT and so forth.
With C —as overloading binary operators in c sharp most modern programming languages—we have the ability to make the operators work with programmer-defined types. This code is simple and concise. We are taking two operands of an assumed numeric type and assigning the value to a overloading binary operators in c sharp variable called a. Programmatically, this is identical to using our operator as shown earlier. That is all that operators truly give us—concise syntax.
So how does this fit into our daily C lives? These were practically hard-wired into our compilers. Now we have the option of using those same operators, but with our own objects as operands. For one reason or another, our application stores each reading in its own object.
That overloading binary operators in c sharp to say Fahrenheit, Celsius and Kelvin are all objects in their own right. So what do we do when we want to display our output in Celsius, given that our inputs are a combination of all three measurements? We need to convert, which typically gives this type of glue code:. Here we are overloading two different types of operators: The only thing to keep in mind when overloading these types of binary operators is that the class that contains them must either be a return value overloading binary operators in c sharp a parameter.
Personally, I like to put these methods in the class of the type they are returning. Again, we are not really doing anything special here. We are simply converting a Celsius value into a Fahrenheit one. The same rules apply here as they do with other operators; the method must be declared in the class that is the return type or the parameter type.
If you want to require the implementers of your class to explicitly cast from type a to type b, then you can replace implicit in the method signature with the keyword explicit. Casting overloading has many great uses. For instance, when populating a business object from an object in a data access layer, I typically write a casting overload within the business object that takes the data object as a parameter.
That way, I keep all the code for populating the business object in the business object itself, rather than having some conversion methods hanging out in limbo. Give it a try sometime. There are many operators in Csome of which require a little special consideration.
The special thing to keep in mind with these is that they are implemented in pairs. In general, operators are great at simplifying those sometimes cumbersome conversion routines and predicates. They also make maintenance a breeze, since you can keep important code in one place and use it everywhere you utilize your class.
One thing to watch out for is overloading binary operators in c sharp your operator overloads. The goal of a software developer should be to write concise and manageable code. Are you at risk? We need to convert, which typically gives this type of glue code: Other Operators There are many operators in Csome of which require a little special consideration.
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