What is appropriate declaration

If you ask for the value to be placed in the variable, that is what happens. Details about bytes, bit patterns, and memory addresses are up to the Java compiler. In the example program, the declaration requests an eight-byte section of memory named payAmount which uses the primitive data type long for representing values.

Where taxes are withheld by the Company on the basis that no Relevant Declaration has been filed with the Company by the Shareholder, Irish legislation does not provide for a refund of tax except in the following circumstances; i. The Company will not have to deduct tax on the occasion of a chargeable event in respect of a Shareholder if a the Shareholder is neither Irish Resident nor Irish Ordinary Resident, b the Shareholder has made a Relevant Declaration and c the Company is not in possession of any information which would reasonably suggest that the information contained therein is not, or is no longer materially correct.

In the absence of a Relevant Declaration or approval from Revenue to operate Equivalent Measures, tax will arise on the happening of a chargeable event in the Company regardless of the fact that a Shareholder is neither Irish Resident nor Irish Ordinary Resident. Usually, argv[0] contains the name of the program, but this is not always the case. Some implementations may allow other types and numbers of parameters; you'd have to check the documentation of your implementation to see what it supports.

You are not required to explicitly write a return statement in main : if you let main return without an explicit return statement, it's the same as if you had written return 0;.

The following two main functions have the same behavior:. The value returned by main is passed to the exit function, which terminates the program. Note that all of this applies only when compiling for a hosted environment informally, an environment where you have a full standard library and there's an OS running your program. It shall have a return type of type int, but otherwise its type is implementation-defined. All implementations shall allow both of the following definitions of main:. In the latter form argc shall be the number of arguments passed to the program from the environment in which the program is run.

If argc is nonzero these arguments shall be supplied in argv[0] through argv[argc-1] as pointers to the initial characters of null-terminated multibyte strings So the following are also permitted:. Any thing else may or may not compile. If main doesn't explicitly return a value, 0 is implicitly returned.

A return statement in main has the effect of leaving the main function destroying any objects with automatic storage duration and calling std::exit with the return value as the argument. If control reaches the end of main without encountering a return statement, the effect is that of executing.

The behavior of std::exit is detailed in section Finally, control is returned to the host environment. Otherwise the status returned is implementation-defined. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow.

Learn more. Ask Question. The optimized behavior is known as call by reference ; it satisfies all of the requirements of the copy-in copy-out model while removing the overhead of copying. Write your code using the model given by copy-in copy-out, without depending on the call-by-reference optimization, so that it behaves correctly with or without the optimization. For more information about memory safety and memory exclusivity, see Memory Safety.

A closure or nested function that captures an in-out parameter must be nonescaping. If you need to capture an in-out parameter without mutating it, use a capture list to explicitly capture the parameter immutably.

If you need to capture and mutate an in-out parameter, use an explicit local copy, such as in multithreaded code that ensures all mutation has finished before the function returns. For more discussion and examples of in-out parameters, see In-Out Parameters.

Parameters can be ignored, take a variable number of values, and provide default values using the following forms:. A parameter with a base type name followed immediately by three dots A parameter that immediately follows a variadic parameter must have an argument label. A function can have multiple variadic parameters. A variadic parameter is treated as an array that contains elements of the base type name.

For example, the variadic parameter Int For an example that uses a variadic parameter, see Variadic Parameters. The given expression is evaluated when the function is called.

If the parameter is omitted when calling the function, the default value is used instead. Methods on an enumeration or a structure that modify self must be marked with the mutating declaration modifier. Methods that override a superclass method must be marked with the override declaration modifier. Methods associated with a type rather than an instance of a type must be marked with the static declaration modifier for enumerations and structures, or with either the static or class declaration modifier for classes.

Several methods that have special names enable syntactic sugar for function call syntax. If a type defines one of these methods, instances of the type can be used in function call syntax.

The function call is understood to be a call to one of the specially named methods on that instance. A class, structure, or enumeration type can support function call syntax by defining a dynamicallyCall withArguments: method or a dynamicallyCall withKeywordArguments: method, as described in dynamicCallable , or by defining a call-as-function method, as described below.

If the type defines both a call-as-function method and one of the methods used by the dynamicCallable attribute, the compiler gives preference to the call-as-function method in circumstances where either method could be used.

The call-as-function methods and the methods from the dynamicCallable attribute make different trade-offs between how much information you encode into the type system and how much dynamic behavior is possible at runtime. The subscript dynamicMember: subscript enables syntactic sugar for member lookup, as described in dynamicMemberLookup.

Functions and methods that can throw an error must be marked with the throws keyword. These functions and methods are known as throwing functions and throwing methods.

They have the following form:. Calls to a throwing function or method must be wrapped in a try or try! As a result, you can use a nonthrowing function in a context where as a throwing one is expected. That said, you can overload a function based on whether a function parameter can throw an error.

That said, a nonthrowing method can override a throwing method, and a nonthrowing method can satisfy a protocol requirement for a throwing method. A function or method can be declared with the rethrows keyword to indicate that it throws an error only if one of its function parameters throws an error.

These functions and methods are known as rethrowing functions and rethrowing methods. Rethrowing functions and methods must have at least one throwing function parameter. A rethrowing function or method can contain a throw statement only inside a catch clause.

This lets you call the throwing function inside a do - catch statement and handle errors in the catch clause by throwing a different error. For example, the following is invalid because the catch clause would handle the error thrown by alwaysThrows. That said, a rethrowing method can override a throwing method, and a rethrowing method can satisfy a protocol requirement for a throwing method. Functions and methods that run asynchronously must be marked with the async keyword.

These functions and methods are known as asynchronous functions and asynchronous methods. Calls to an asynchronous function or method must be wrapped in an await expression—that is, they must be in the scope of an await operator. As a result, you can use a synchronous function in a context where an asynchronous function is expected.

For example, you can override an asynchronous method with a synchronous method, and a synchronous method can satisfy a protocol requirement that requires an asynchronous method. Functions and methods with the Never return type are called nonreturning. Nonreturning functions and methods either cause an irrecoverable error or begin a sequence of work that continues indefinitely. This means that code that would otherwise run immediately after the call is never executed.

A nonreturning function or method can be called to conclude the else clause of a guard statement, as discussed in Guard Statement. You can override a nonreturning method, but the new method must preserve its return type and nonreturning behavior. Enumeration declarations have two basic forms and are declared using the enum keyword.

The body of an enumeration declared using either form contains zero or more values—called enumeration cases —and any number of declarations, including computed properties, instance methods, type methods, initializers, type aliases, and even other enumeration, structure, class, and actor declarations.

Initializers can delegate to other initializers in the enumeration, but the initialization process is complete only after an initializer assigns one of the enumeration cases to self. Like structures but unlike classes, enumerations are value types; instances of an enumeration are copied when assigned to variables or constants, or when passed as arguments to a function call. You can extend the behavior of an enumeration type with an extension declaration, as discussed in Extension Declaration.

Enumerations declared in this form are sometimes called discriminated unions in other programming languages. In this form, each case block consists of the case keyword followed by one or more enumeration cases, separated by commas. The name of each case must be unique. Each case can also specify that it stores values of a given type. These types are specified in the associated value types tuple, immediately following the name of the case.

Enumeration cases that store associated values can be used as functions that create instances of the enumeration with the specified associated values. And just like functions, you can get a reference to an enumeration case and apply it later in your code. For more information and to see examples of cases with associated value types, see Associated Values.

Enumerations can have a recursive structure, that is, they can have cases with associated values that are instances of the enumeration type itself. However, instances of enumeration types have value semantics, which means they have a fixed layout in memory. To support recursion, the compiler must insert a layer of indirection. To enable indirection for a particular enumeration case, mark it with the indirect declaration modifier.

An indirect case must have an associated value. To enable indirection for all the cases of an enumeration that have an associated value, mark the entire enumeration with the indirect modifier—this is convenient when the enumeration contains many cases that would each need to be marked with the indirect modifier. The following form declares an enumeration type that contains enumeration cases of the same basic type:.

In this form, each case block consists of the case keyword, followed by one or more enumeration cases, separated by commas. Unlike the cases in the first form, each case has an underlying value, called a raw value , of the same basic type. The type of these values is specified in the raw-value type and must represent an integer, floating-point number, string, or single character.

In particular, the raw-value type must conform to the Equatable protocol and one of the following protocols: ExpressibleByIntegerLiteral for integer literals, ExpressibleByFloatLiteral for floating-point literals, ExpressibleByStringLiteral for string literals that contain any number of characters, and ExpressibleByUnicodeScalarLiteral or ExpressibleByExtendedGraphemeClusterLiteral for string literals that contain only a single character.

Each case must have a unique name and be assigned a unique raw value. In the above example, the raw value of ExampleEnum. And because the value of ExampleEnum.

In the above example, the raw value of GamePlayMode. Enumerations that have cases of a raw-value type implicitly conform to the RawRepresentable protocol, defined in the Swift standard library. As a result, they have a rawValue property and a failable initializer with the signature init? You can use the rawValue property to access the raw value of an enumeration case, as in ExampleEnum. For more information and to see examples of cases with raw-value types, see Raw Values.

To reference the case of an enumeration type, use dot. When the enumeration type can be inferred from context, you can omit it the dot is still required , as described in Enumeration Syntax and Implicit Member Expression. To check the values of enumeration cases, use a switch statement, as shown in Matching Enumeration Values with a Switch Statement. The enumeration type is pattern-matched against the enumeration case patterns in the case blocks of the switch statement, as described in Enumeration Case Pattern.

A structure declaration introduces a named structure type into your program. Structure declarations are declared using the struct keyword and have the following form:.

The body of a structure contains zero or more declarations. These declarations can include both stored and computed properties, type properties, instance methods, type methods, initializers, subscripts, type aliases, and even other structure, class, actor, and enumeration declarations.

For a discussion and several examples of structures that include various kinds of declarations, see Structures and Classes. Properties of a structure instance can be accessed using dot. Structures are value types; instances of a structure are copied when assigned to variables or constants, or when passed as arguments to a function call.

You can extend the behavior of a structure type with an extension declaration, as discussed in Extension Declaration. A class declaration introduces a named class type into your program. Class declarations are declared using the class keyword and have the following form:. The body of a class contains zero or more declarations. These declarations can include both stored and computed properties, instance methods, type methods, initializers, a single deinitializer, subscripts, type aliases, and even other class, structure, actor, and enumeration declarations.

For a discussion and several examples of classes that include various kinds of declarations, see Structures and Classes.

A class type can inherit from only one parent class, its superclass , but can adopt any number of protocols. The superclass appears first after the class name and colon, followed by any adopted protocols.