Breeze annotation-Swift programming language: Point11 ~ 15,-swiftpoint11

Breeze annotation-Swift programming language: Point11 ~ 15,-swiftpoint11

Directory Index

Breeze annotation-Swift Programming Language

Point 11.

Numeric literal

Code example:

Let decimalInteger = 17 // decimal 17let binaryInteger = 0b10001 // binary 17let octalInteger = 0o21 // 17let hexadecimalInteger of octal = 0x11 // 17 of hexadecimal format

Note:

• Integer literal can be written as follows: decimal number without prefix; binary number, Prefix: 0b; octal number, Prefix: 0o; hexadecimal number, Prefix: 0x.
• The floating point literal can be decimal (without a prefix) or hexadecimal (with a prefix of 0x ).
• A floating point literal must have at least one decimal number (or a hexadecimal number) on both sides of the decimal point ).
• The literal number of a decimal floating point has an optional index, which is specified by e in upper or lower case.
• The hexadecimal floating point literal must contain an index, which is specified by p in upper or lower case.

• Let decimalDouble = 17.2e0 // 17.2let hexadecimalDouble = 0x11. 2p0 // 17.125 Of The hexadecimal floating point number

• If the exponent of a decimal number is exp, the number is equivalent to the product of base number and 10 ^ exp.
• If the exponent of a hexadecimal number is exp, the number is equivalent to the product of the base number and 2 ^ exp.
• The literal numbers of integers and floating-point numbers can contain additional formats (0 and underline) to enhance readability. These formats (0 and underline) do not affect the actual literal values.

• let paddedDouble = 000123.456let oneMillion = 1_000_000let justOverOneMillion = 1_000_000.000_000_1

 

Point 12.

Numeric type conversion

Code example:

let twoThousand: UInt16 = 2_000let one: UInt8 = 1let twoThousandAndOne = twoThousand + UInt16(one) 

Note:

• Generally, even if the Integer constants and variables in the Code are known to be non-negative, use the Int type.
• By using the default Integer type, you can ensure that the Integer constants and variables can be reused directly, and can match the type inference of the integer literal.
• When explicitly specified data types are used, value overflow can be detected in a timely manner and special data is being processed.
• Variables and constants of different integer types can store numbers of different ranges.
• If the number is out of the storage range of constants or variables, an error is reported during compilation.
• Since each integer type can store values of different ranges, You must select numeric type conversion based on different situations.
• The type conversion method can be used to prevent implicit conversion errors and clarify the type conversion intent in your code.
• To convert one numeric type to another, use the current value to initialize a new expected numeric type, which is the target type.
• The type must be explicitly specified for integer and floating-point conversions.

• let three = 3let pointOneFourOneFiveNine = 0.14159let pi = Double(three) + pointOneFourOneFiveNine

• When a floating point is converted to an integer, the floating point value (decimal part) is truncated.

 

Point 13.

Type alias

Code example:

Typealias AudioSample = UInt16 // The type alias of UInt16 is defined as AudioSamplevar maxAmplitudeFound = AudioSample. min // maxAmplitudeFound is now 0

Note:

• A type alias defines another name for an existing type.
• Use the typealias keyword to define the type alias.
• After defining a type alias, you can use the alias wherever the original name can be used.

 

Point 14.

Boolean Value

Code example:

Let orangesAreOrange = true // The value is true, and the value is false.

Note:

• A boolean value is a logical true or false value.
• Swift has two Boolean constants: true and false.
• If a non-Boolean value is used where the Bool type is required, the Swift type Security Mechanism reports an error.

 

Point 15.

Tuples

Code example:

// The type of http404Error is (Int, String), and the value is (404, "Not Found") let http404Error = (404, "Not Found ")

Note:

• Tuples combine multiple values into a composite value.
• The values in the meta-group can be of any type, but they do not need to be of the same type, and the order of the types is also arbitrary.
• The content of tuples can be divided into separate constants and variables, and then you can use them normally.

• Let (statusCode, statusMessage) = http404Error // output "The status code is 404" println ("The status code is \ (statusCode )") // output "The status message is Not Found" println ("The status message is \ (statusMessage )")

• If you only need a portion of the values of the tuples, you can mark the ignored parts with underscores.

• Let (justTheStatusCode, _) = http404Error // output "The status code is 404" println ("The status code is \ (justTheStatusCode )")

• You can use subscript to access a single element in a tuples. The subscript starts from scratch.

• // Output "The status code is 404" println ("The status code is \ (http404Error. 0) ") // output" The status message is Not Found "println (" The status message is \ (http404Error. 1 )")

• You can name a single element when defining the tuples, and obtain the value of the element through the element name.

• Let http200Status = (statusCode: 200, description: "OK") // output "The status code is 200" println ("The status code is \ (http200Status. statusCode) ") // output" The status message is OK "println (" The status message is \ (http200Status. description )")

• Tuples can be used as function return values.

 

Author: Qingfeng fuliu (DashGeng)

Source: http://www.cnblogs.com/dashgeng/

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