Fortran匯出資料型別

Fortran語言可以定義匯出的資料型別。匯出的資料型別也被稱為一個結構，它可以包含不同型別的資料物件。

匯出的資料型別被用來代表一個記錄。例如要跟蹤在圖書館的書，可能希望跟蹤的每本書有如下屬性：

• 標題- Title
• 作者 - Author
• 科目 - Subject
• 編號 - Book ID

定義一個匯出的資料型別

定義一個派生資料型別，型別和端型別的語句被使用。型別語句定義了一個新的資料型別，專案不止一個成員。型別宣告的格式是這樣的：

type type_name      
   declarations
end type 

這裡是會宣告書的結構方式：

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

存取結構成員

一個派生資料型別的物件被稱為結構

型別書籍(Books) 的結構像一個型別宣告語句建立如下：

type(Books) :: book1 

結構的組成部分可以使用該元件選擇字元(%)進行存取 :

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

請注意，％符號前後沒有空格。

範例

下面的程式說明了上述概念：

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

當上述程式碼被編譯和執行時，它產生了以下結果：

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

結構陣列

還可以建立一個派生型別的陣列：

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

陣列的單個元素，可以存取如下：

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

下面的程式說明了這個概念：

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

當上述程式碼被編譯和執行時，它產生了以下結果：

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