Fortran 派生数据类型

Fortran 让您定义派生数据类型。派生数据类型也称为结构，它可以由不同类型的数据对象组成。

派生数据类型用于表示记录。例如，如果你想跟踪图书馆里的书，你可能想跟踪每本书的以下属性：

• Title
• Author
• Subject
• Book ID

定义派生数据类型

要定义派生数据类型，请使用类型和结束类型语句。type 语句定义了一个新的数据类型，程序有多个成员。类型语句的格式如下：

type type_name
   declarations
end type

以下是您声明 Book 结构的方式：

type Books
   character(len = 50) :: title
   character(len = 50) :: author
   character(len = 150) :: subject
   integer :: book_id
end type Books

访问结构成员

派生数据类型的对象称为结构。

可以在类型声明语句中创建 Books 类型的结构，如下所示：

type(Books) :: book1

可以使用组件选择器字符（%）访问结构的组件：

book1%title = "C Programming"
book1%author = "Nuha Ali"
book1%subject = "C Programming Tutorial"
book1%book_id = 6495407

实例

program deriveDataType
   !type declaration
   type Books
      character(len = 50) :: title
      character(len = 50) :: author
      character(len = 150) :: subject
      integer :: book_id
   end type Books
   !declaring type variables
   type(Books) :: book1
   type(Books) :: book2
   !accessing the components of the structure
   book1%title = "C Programming"
   book1%author = "Nuha Ali"
   book1%subject = "C Programming Tutorial"
   book1%book_id = 6495407 
   book2%title = "Telecom Billing"
   book2%author = "Zara Ali"
   book2%subject = "Telecom Billing Tutorial"
   book2%book_id = 6495700
   !display book info
   Print *, book1%title
   Print *, book1%author
   Print *, book1%subject
   Print *, book1%book_id
   Print *, book2%title
   Print *, book2%author
   Print *, book2%subject
   Print *, book2%book_id
end program deriveDataType

结果如下：

C Programming
 Nuha Ali
 C Programming Tutorial
   6495407
 Telecom Billing
 Zara Ali
 Telecom Billing Tutorial
   6495700

结构数组

您还可以创建派生类型的数组：

type(Books), dimension(2) :: list

数组的各个元素可以按以下方式访问：

list(1)%title = "C Programming"
list(1)%author = "Nuha Ali"
list(1)%subject = "C Programming Tutorial"
list(1)%book_id = 6495407

实例

program deriveDataType
   !type declaration
   type Books
      character(len = 50) :: title
      character(len = 50) :: author
      character(len = 150) :: subject
      integer :: book_id
   end type Books
   !declaring array of books
   type(Books), dimension(2) :: list
   !accessing the components of the structure
   list(1)%title = "C Programming"
   list(1)%author = "Nuha Ali"
   list(1)%subject = "C Programming Tutorial"
   list(1)%book_id = 6495407 
   list(2)%title = "Telecom Billing"
   list(2)%author = "Zara Ali"
   list(2)%subject = "Telecom Billing Tutorial"
   list(2)%book_id = 6495700
   !display book info
   Print *, list(1)%title
   Print *, list(1)%author
   Print *, list(1)%subject
   Print *, list(1)%book_id
   Print *, list(1)%title
   Print *, list(2)%author
   Print *, list(2)%subject
   Print *, list(2)%book_id
end program deriveDataType

结果如下：

C Programming
Nuha Ali
C Programming Tutorial
   6495407
C Programming
Zara Ali
Telecom Billing Tutorial
   6495700