Fortran 字符串

Fortran 语言可以将字符视为单个字符或连续字符串。

字符串的长度可能只有一个字符，甚至可能为 0。在 Fortran 中，字符常数在双引号或单引号之间给出。

内部数据类型字符存储字符和字符串。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。您可以按位置引用字符串中的单个字符；最左侧的字符位于位置 1。

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

也可以这样赋值：

character (len = 40) :: name
name = "Zara Ali"

以下实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

结果为：

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

连接字符串

连接运算符 // 用于连接字符串。

以下实例演示了这一点：

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

结果为：

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

提取子字符串

在 Fortran 中，您可以通过对字符串进行索引来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。这被称为范围说明符。

以下实例显示了如何从字符串 "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

结果为：

World

实例

以下实例使用 date_and_time 函数给出日期和时间字符串。我们使用范围说明符分别提取年、日期、月、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

结果为：

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

裁剪字符串

trim 函数接受一个字符串，并在删除所有尾随空格后返回输入字符串。

实例

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

结果为：

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

字符串左右调整函数 adjustl 接受一个字符串，并通过删除前导空格并将其作为尾随空格附加来返回它。

函数 adjuster 接受一个字符串，并通过删除尾随空格并将其作为前导空格附加来返回它。

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

结果为：

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，则返回一个整数，该整数是第一个字符中第二个字符的起始索引，否则返回 0。

实例

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

结果为：

test is found at index: 11