Breeze annotation-Swift programming language: Point6 ~ 10,-swiftpoint6

Breeze annotation-Swift programming language: Point6 ~ 10,-swiftpoint6

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Breeze annotation-Swift Programming Language

Point 6.

Output constants and variables

Code example:

// The output content will wrap println ("hello, world") // The output content will not wrap print ("My name is Dash Geng") at the end ")

Note:

• You can use the println or print function to output the value of the current constant or variable.
• Println and print are global functions used for output (built-in functions ).
• The output content of the println function is wrapped in a line break.
• The output content of the print function does not last wrap.
• Swift uses string interpolation to add a constant or variable name to a long string as a placeholder. During code execution, these Placeholders are replaced with the values of the current constant or variable.

 

Point 7.

Swift code comment

Code example:

/* Swift comments include multiline comments (/**/) and single-line comments (//) /* multi-line comments can be nested with multi-line comments * // single-line comments can also be nested with multi-line comments */

Note:

• Like other languages, the Swift compiler automatically ignores comments when compiling code.
• Swift has two annotation styles: single-line comment and multi-line comment.
• Single line comment with Double Forward slash (//.
• The start of a multi-line comment is marked as a single forward slash followed by an asterisk (/*), Ending with an asterisk followed by a single forward slash (*/).
• Swift multi-line comments can contain single-line comments or nested multi-line comments.

 

Point 8.

Integer type

Code example:

// Signed integer var temperature: Int8 =-8var height: Int16 = 179var monthlyExpenditure: Int32 =-4680var landArea: Int64 = 9_600_000 // unsigned integer var age: UInt8 = 32var years: UInt16 = 2014var moonDistance: UInt32 = 384400var globalPopulation: UInt64 = 7_000_000_000

Note:

• An integer is a number without decimal digits.
• Swift provides 8, 16, 32, and 64-Bit Signed and unsigned integer types.
• Signed integer type: Int, Int8, Int16, Int32, Int64.
• Unsigned integer type: UInt, UInt8, UInt16, UInt32, UInt64.
• All data types of Swift use the upper-case naming method.
• You can access the min and max attributes of different integer types to obtain the maximum and minimum values of the corresponding type.

• // Minimum value of the 16-bit signed number:-32768let minInt16Num: Int16 = Int16.min // minimum value of the 16-bit unsigned number: 0let minUInt16Num: UInt16 = UInt16.min // maximum value of a 32-bit signed integer: 2_147_483_647let maxInt32Num: Int32 = Int32.max // maximum value of a 32-bit unsigned integer: 4_294_967_295let maxUInt32Num: UInt32 = UInt32.max

• Swift provides a special integer Int with the same length as the native character of the current platform. On 32-bit platforms, Int and Int32 are of the same length. On 64-bit platforms, Int and Int64 are of the same length.

• /* The length of the Int type depends on the current CPU font length, and the local font length is 64 bits. Therefore, maxIntNum is 9_223_372_036_854_775_807 */let maxIntNum: Int = Int. max

• Swift also provides a special unsigned UInt with the same length as the native character of the current platform. On a 32-bit platform, the length of UInt is the same as that of UInt32. On a 64-bit platform, the length of UInt is the same as that of UInt64.

• /* The length of the UInt type depends on the current CPU length, and the local font length is 64 bits. Therefore, maxUIntNum is: 18_446_744_073_709_550000615 */let maxUIntNum: UInt = UInt. max

• Do not use UInt, but use Int in a unified manner. This improves code reusability, avoids conversion between different types of numbers, and matches the type inference of numbers.

 

Point 9.

Floating Point Type

Code example:

Var floatNum: Float = 1.12345678901234567890var float32Num: Float32 = 1.12345678901234567890var float64Num: Float64 = 1.12345678901234567890var float80Num: Float80 = 1.12345678901234567890var doubleNum: Double = 1.12345678901234567890 // The value of floatNum is: 1.123 _ percentile ("\ (floatNum)") // The value of float32Num is 1.123 _ 456_835_746_77println ("\ (float32Num)") // The value of float64Num is: 1.123 _ percentile ("\ (float64Num)") // The value of float80Num is 1.123 _ 456_789_012_35println ("\ (float80Num)") // The value of doubleNum is: 1.123 _ 456_789_012_35println ("\ (doubleNum )")

Note:

• A floating point number is a number with a decimal part.
• The floating point type has a larger range than the integer type. It can store numbers that are larger or smaller than the Int type.
• Swift provides two types of signed floating point numbers: Double and Float.
• Float indicates a 32-bit floating point number, and Double indicates a 64-bit floating point number.
• Float is accurate to 6 digits, and Double is accurate to at least 15 digits.
• In fact, Swift has five optional types of signed floating point numbers: Float, Float32, Float64, Float80, and Double.
• On a 64-bit processor, Float and Float32 have the same value range. Float64, Float80, and Double have the same value range.

 

Point 10.

Type security and type inference

Code example:

// The assignment of constants or variables triggers type inference. // Type inference the positive integer is inferred as Int type var index = 1 // type inference the floating point is inferred as Double type var pai = 3.14

Note:

• Swift is a type-safe language. The Type-safe language allows you to clearly understand the type of the value to be processed by the Code.
• Because Swift is type-safe, it performs type checks during code compilation and marks mismatched types as errors.
• If the type is not explicitly specified, Swift uses type inference to select the appropriate type.
• When declaring constants or variables, assign them a literal to trigger type inference.
• Type inference infers Positive Integers to the Int type and floating point numbers to the Double type.

Author: Qingfeng fuliu (DashGeng)

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

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