Fortran - 字符

Fortran 语言可以将字符视为单个字符或连续的字符串。

字符可以是取自基本字符集的任何符号，即取自字母、十进制数字、下划线和 21 个特殊字符。

字符常量是固定值的字符串。

内在数据类型character存储字符和字符串。 字符串的长度可以通过 len 说明符指定。 如果没有指定长度，则为 1。您可以通过位置引用字符串中的单个字符； 最左边的字符位于位置 1。

字符声明

声明字符类型数据与其他变量相同 −

type-specifier :: variable_name

例如，

character :: reply, sex

您可以分配一个值，例如，

reply = ‘N’ 
sex = ‘F’

下面的例子演示了字符数据类型的声明和使用 −

program hello
implicit none

   character(len = 15) :: surname, firstname 
   character(len = 6) :: title 
   character(len = 25)::greetings
   
   title = 'Mr. ' 
   firstname = 'Rowan ' 
   surname = 'Atkinson'
   greetings = 'A big hello from Mr. Bean'
   
   print *, 'Here is ', title, firstname, surname
   print *, greetings
   
end program hello

当你编译并执行上面的程序时，它会产生以下结果 −

Here is Mr. Rowan Atkinson       
A big hello from Mr. Bean

字符串联

连接运算符//，连接字符。

以下示例演示了这一点 −

program hello
implicit none

   character(len = 15) :: surname, firstname 
   character(len = 6) :: title 
   character(len = 40):: name
   character(len = 25)::greetings
   
   title = 'Mr. ' 
   firstname = 'Rowan ' 
   surname = 'Atkinson'
   
   name = title//firstname//surname
   greetings = 'A big hello from Mr. Bean'
   
   print *, 'Here is ', name
   print *, greetings
   
end program hello

当你编译并执行上面的程序时，它会产生以下结果 −

Here is Mr.Rowan Atkinson       
A big hello from Mr.Bean

一些字符函数

下表显示了一些常用的字符函数及其说明 −

示例 1

此示例展示了index函数的使用 −

program testingChars
implicit none

   character (80) :: text 
   integer :: i 
   
   text = 'The intrinsic data type character stores characters and   strings.'
   i=index(text,'character') 
   
   if (i /= 0) then
      print *, ' The word character found at position ',i 
      print *, ' in text: ', text 
   end if
   
end program testingChars

当你编译并执行上面的程序时，它会产生以下结果 −

The word character found at position 25
in text : The intrinsic data type character stores characters and strings.  

示例 2

此示例演示了trim函数的使用 −

program hello
implicit none

   character(len = 15) :: surname, firstname 
   character(len = 6) :: title 
   character(len = 25)::greetings
   
   title = 'Mr.' 
   firstname = 'Rowan' 
   surname = 'Atkinson'
   
   print *, 'Here is', title, firstname, surname
   print *, 'Here is', trim(title),' ',trim(firstname),' ', trim(surname)
   
end program hello

当你编译并执行上面的程序时，它会产生以下结果 −

 Here isMr.   Rowan          Atkinson       
 Here isMr. Rowan Atkinson

示例 3

此示例演示了achar函数的使用 −

program testingChars
implicit none

   character:: ch
   integer:: i
   
   do i = 65, 90
      ch = achar(i)
      print*, i, ' ', ch
   end do
   
end program testingChars

当你编译并执行上面的程序时，它会产生以下结果 −

65  A
66  B
67  C
68  D
69  E
70  F
71  G
72  H
73  I
74  J
75  K
76  L
77  M
78  N
79  O
80  P
81  Q
82  R
83  S
84  T
85  U
86  V
87  W
88  X
89  Y
90  Z

检查字符的词汇顺序

以下函数确定字符的词汇序列 −

示例 4

以下函数演示了使用 −

program testingChars
implicit none

   character:: a, b, c
   a = 'A'
   b = 'a'
   c = 'B'
   
   if(lgt(a,b)) then
      print *, 'A is lexically greater than a'
   else
      print *, 'a is lexically greater than A'
   end if
   
   if(lgt(a,c)) then
      print *, 'A is lexically greater than B'
   else
      print *, 'B is lexically greater than A'
   end if  
   
   if(llt(a,b)) then
      print *, 'A is lexically less than a'
   end if
   
   if(llt(a,c)) then
      print *, 'A is lexically less than B'
   end if
   
end program testingChars

当你编译并执行上面的程序时，它会产生以下结果 −

a is lexically greater than A
B is lexically greater than A
A is lexically less than a
A is lexically less than B