Fortran - 字符串

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Fortran 语言可以将字符视为单个字符或连续字符串。

字符字符串的长度可以只有一个字符，甚至可以为零长度。在 Fortran 中，字符常量用一对双引号或单引号括起来。

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。如果未指定长度，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。

字符串声明

声明字符串与声明其他变量相同：

type-specifier :: variable_name

例如：

Character(len = 20) :: firstname, surname

您可以赋值如下：

character (len = 40) :: name  
name = “Zara Ali”

以下示例演示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. Beans'
   
   print *, 'Here is', title, firstname, surname
   print *, greetings
   
end program hello

编译并执行上述程序后，将产生以下结果：

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

字符串连接

连接运算符 // 用于连接字符串。

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. Beans'
   
   print *, 'Here is', name
   print *, greetings
   
end program hello

编译并执行上述程序后，将产生以下结果：

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

提取子字符串

在 Fortran 中，您可以通过索引字符串来提取字符串中的子字符串，在一对括号中给出子字符串的起始和结束索引。这称为范围说明符。

以下示例演示如何从字符串“hello world”中提取子字符串“world”：

program subString

   character(len = 11)::hello
   hello = "Hello World"
   print*, hello(7:11)
   
end program subString 

编译并执行上述程序后，将产生以下结果：

World

示例

以下示例使用date_and_time函数来获取日期和时间字符串。我们使用范围说明符分别提取年份、日期、月份、小时、分钟和秒信息。

program  datetime
implicit none

   character(len = 8) :: dateinfo ! ccyymmdd
   character(len = 4) :: year, month*2, day*2

   character(len = 10) :: timeinfo ! hhmmss.sss
   character(len = 2)  :: hour, minute, second*6

   call  date_and_time(dateinfo, timeinfo)

   !  let’s break dateinfo into year, month and day.
   !  dateinfo has a form of ccyymmdd, where cc = century, yy = year
   !  mm = month and dd = day

   year  = dateinfo(1:4)
   month = dateinfo(5:6)
   day   = dateinfo(7:8)

   print*, 'Date String:', dateinfo
   print*, 'Year:', year
   print *,'Month:', month
   print *,'Day:', day

   !  let’s break timeinfo into hour, minute and second.
   !  timeinfo has a form of hhmmss.sss, where h = hour, m = minute
   !  and s = second

   hour   = timeinfo(1:2)
   minute = timeinfo(3:4)
   second = timeinfo(5:10)

   print*, 'Time String:', timeinfo
   print*, 'Hour:', hour
   print*, 'Minute:', minute
   print*, 'Second:', second   
   
end program  datetime

编译并执行上述程序后，将提供详细的日期和时间信息：

Date String: 20140803
Year: 2014
Month: 08
Day: 03
Time String: 075835.466
Hour: 07
Minute: 58
Second: 35.466

修剪字符串

trim函数接收一个字符串，并在删除所有尾随空格后返回输入字符串。

示例

program trimString
implicit none

   character (len = *), parameter :: fname="Susanne", sname="Rizwan"
   character (len = 20) :: fullname 
   
   fullname = fname//" "//sname !concatenating the strings
   
   print*,fullname,", the beautiful dancer from the east!"
   print*,trim(fullname),", the beautiful dancer from the east!"
   
end program trimString

编译并执行上述程序后，将产生以下结果：

Susanne Rizwan      , the beautiful dancer from the east!
 Susanne Rizwan, the beautiful dancer from the east!

字符串的左对齐和右对齐

函数adjustl接收一个字符串，并通过删除前导空格并在末尾附加它们来返回该字符串。

函数adjustr接收一个字符串，并通过删除尾随空格并在开头附加它们来返回该字符串。

示例

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'
   greetings = 'A big hello from Mr. Beans'
   
   name = adjustl(title)//adjustl(firstname)//adjustl(surname)
   print *, 'Here is', name
   print *, greetings
   
   name = adjustr(title)//adjustr(firstname)//adjustr(surname)
   print *, 'Here is', name
   print *, greetings
   
   name = trim(title)//trim(firstname)//trim(surname)
   print *, 'Here is', name
   print *, greetings
   
end program hello

编译并执行上述程序后，将产生以下结果：

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

在字符串中搜索子字符串

index 函数接收两个字符串，并检查第二个字符串是否为第一个字符串的子字符串。如果第二个参数是第一个参数的子字符串，则它返回一个整数，该整数是第二个字符串在第一个字符串中的起始索引，否则它返回零。

示例

program hello
implicit none

   character(len=30) :: myString
   character(len=10) :: testString
   
   myString = 'This is a test'
   testString = 'test'
   
   if(index(myString, testString) == 0)then
      print *, 'test is not found'
   else
      print *, 'test is found at index: ', index(myString, testString)
   end if
   
end program hello

编译并执行上述程序后，将产生以下结果：

test is found at index: 11