Fortran字符串 - Fortran教程
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