Strings（ Strings）

Fortran语言可以将字符视为单个字符或连续字符串。

字符串的长度可以只有一个字符，或者甚至可以是零长度。 在Fortran中，字符常量在一对双引号或单引号之间给出。

内在数据类型character存储字符和字符串。 字符串的长度可以由len specifier 。 如果未指定长度，则为1.您可以按位置引用字符串中的单个字符; 最左边的字符位于第1位。

字符串声明

声明字符串与其他变量相同 -

type-specifier :: variable_name

例如，

Character(len = 20) :: firstname, surname

你可以分配一个值，如，

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

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

编译并执行上述程序时，会产生以下结果 -

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

字符串连接 (String Concatenation)

连接运算符//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时，会产生以下结果 -

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从字符串中提取子字符串，在一对括号中给出子字符串的开始和结束索引。 这称为范围说明符。

以下示例显示如何从字符串'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时，会产生以下结果 -

World

例子 (Example)

以下示例使用date_and_time函数来提供日期和时间字符串。 我们使用范围说明符分别提取年份，日期，月份，小时，分钟和第二个信息。

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

当您编译并执行上述程序时，它会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函数接受一个字符串，并在删除所有尾随空白后返回输入字符串。

例子 (Example)

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时，会产生以下结果 -

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

字符串的左右调整

函数adjustl接受一个字符串并通过删除前导空格并将它们作为尾随空格附加来返回它。

函数adjustr接受一个字符串并通过删除尾随空白并将它们作为前导空格附加来返回它。

例子 (Example)

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时，会产生以下结果 -

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函数接受两个字符串并检查第二个字符串是否是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，该整数是第一个字符串中第二个字符串的起始索引，否则返回零。

例子 (Example)

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时，会产生以下结果 -

test is found at index: 11