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📜  Fortran-字符串

📅  最后修改于: 2020-11-04 06:16:33             🧑  作者: Mango

Fortran语言可以将字符视为单个字符或连续的字符串。

的可以是唯一一个在长度字符，或者它甚至可以是零长度的。在Fortran中，字符常量在一对双引号或单引号之间给出。

固有数据类型字符存储字符和字符串。字符串的长度可以由len specifier指定。如果未指定长度，则为1。可以按位置引用字符串的各个字符；否则，可以为0。最左边的字符在位置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

您可以分配一个值，例如

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-

现场演示
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

当您编译并执行上述程序时，它将产生以下结果-

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

字符串串联

串联运算符// //串联字符串。

以下示例演示了这一点-

现场演示
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

当您编译并执行上述程序时，它将产生以下结果-

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

提取子串

在Fortran中，可以通过对字符串进行索引来从字符串提取子字符串，在一对方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”-

现场演示
program subString

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

当您编译并执行上述程序时，它将产生以下结果-

World

例

以下示例使用date_and_time函数提供日期和时间字符串。我们使用范围说明符分别提取年，日，月，时，分和秒信息。

现场演示
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

修整弦

trim函数采用字符串，并在删除所有尾随空格后返回输入字符串。

例

现场演示
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

当您编译并执行上述程序时，它将产生以下结果-

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

琴弦的左右调节

函数Adjustl接受一个字符串，并通过删除前导空格并将其附加为尾随空格来返回它。

函数调节器获取一个字符串，并通过删除尾随空格并将它们附加为前导空格来返回它。

例

现场演示
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

当您编译并执行上述程序时，它将产生以下结果-

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函数采用两个字符串，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，该整数是第二个字符串在第一个字符串的起始索引，否则返回零。

例

现场演示
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

当您编译并执行上述程序时，它将产生以下结果-

test is found at index: 11