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Fortran字符串

Fortran语言可以把字符作为单个字符或连续的字符串。

字符串可以是只有一个长度的字符,或者它甚至可以是零长度。在Fortran语言,字符常量是一对双引号或单引号之间字符内容。

内部数据类型的字符存储字符和字符串。字符串的长度可以通过len个符来指定。如果没有指定长度,它是长度是1. 可以将字符串按位置指的是指在单个字符;最左边的字符的位置是1。

字符串声明

声明一个字符串跟其他变量是一样的:

type-specifier :: variable_name

例如,

Character(len=20) :: firstname, surname

可以指定一个值类似,

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

下面的例子演示了声明和使用字符数据类型:

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

当编译并执行上述程序,将产生以下结果:

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

字符串连接

连接运算符//,连接字符串。

下面的例子说明了这一点:

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

当编译并执行上述程序,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,可以通过索引的字符串,开始和子串一对括号的结束索引,从字符串中提取一个子字符串。这就是所谓的范围说明。

下面的示例显示了如何提取字符串'Hello World'的子字符串“world”:

program subString

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

当编译并执行上述程序,将产生以下结果:

World

例子

下面的示例使用 date_and_time 函数,得到日期和时间的字符串。我们使用范围说明符单独提取年份,日期,月份,小时,分钟和秒的信息。

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

当编译并执行上述程序,它提供了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

字符串修整

trim函数接受一个字符串,并删除所有尾随空格后返回输入字符串。

例子

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

当编译并执行上述程序,将产生以下结果:

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

字符串左右调整

函数 adjustl 需要一个字符串,并通过去除前导空格,并追加其作为尾随空白返回。

函数 adjustr 需要一个字符串,并通过删除尾随空格和追加作为前导空格返回。

例子

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

当编译并执行上述程序,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

搜索字符串的子串

index 函数有两个字符串,并检查是否第二个字符串的第一个字符串的子串。如果第二个参数是第一个参数的子字符串,然后返回一个整数,是第一个字符串第二个字符串的开始索引,否则返回零。

例子

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

当编译并执行上述程序,将产生以下结果:

test is found at index: 11