Fortran 简明教程

Fortran - Characters

Fortran 语言可以将字符视为单个字符或连续字符串。

The Fortran language can treat characters as single character or contiguous strings.

字符可以是取自基本字符集的任何符号，即取自字母、十进制数字、下划线和 21 个特殊字符。

Characters could be any symbol taken from the basic character set, i.e., from the letters, the decimal digits, the underscore, and 21 special characters.

字符常量是固定值字符字符串。

A character constant is a fixed valued character string.

固有数据类型 @ {s5} 存储字符和字符串。字符串长度可以用 @ {s6} 说明符指定。如果未指定长度，则为 1。您可以按位置引用字符串中的各个字符；最左边的字符位于位置 1。

The intrinsic data type character stores characters and strings. The length of the string can be specified by len specifier. If no length is specified, it is 1. You can refer individual characters within a string referring by position; the left most character is at position 1.

Character Declaration

声明字符类型数据与其他变量相同 −

Declaring a character type data is same as other variables −

type-specifier :: variable_name

例如，

For example,

character :: reply, sex

您可以分配值，例如，

you can assign a value like,

reply = ‘N’
sex = ‘F’

以下示例演示了字符数据类型的声明和使用−

The following example demonstrates declaration and use of character data type −

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. Bean'

   print *, 'Here is ', title, firstname, surname
   print *, greetings

end program hello

当您编译并执行以上程序时，将生成以下结果——

When you compile and execute the above program it produces the following result −

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

Concatenation of Characters

连接运算符 // 连接字符。

The concatenation operator //, concatenates characters.

以下示例演示了这一点−

The following example demonstrates this −

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. Bean'

   print *, 'Here is ', name
   print *, greetings

end program hello

当您编译并执行以上程序时，将生成以下结果——

When you compile and execute the above program it produces the following result −

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

Some Character Functions

下表显示了一些常用的字符函数以及描述−

The following table shows some commonly used character functions along with the description −

Sr.No

Function & Description

1

len(string) It returns the length of a character string

2

index(string,sustring) It finds the location of a substring in another string, returns 0 if not found.

3

achar(int) It converts an integer into a character

4

iachar(c) It converts a character into an integer

5

trim(string) It returns the string with the trailing blanks removed.

6

scan(string, chars) It searches the "string" from left to right (unless back=.true.) for the first occurrence of any character contained in "chars". It returns an integer giving the position of that character, or zero if none of the characters in "chars" have been found.

7

verify(string, chars) It scans the "string" from left to right (unless back=.true.) for the first occurrence of any character not contained in "chars". It returns an integer giving the position of that character, or zero if only the characters in "chars" have been found

8

adjustl(string) It left justifies characters contained in the "string"

9

adjustr(string) It right justifies characters contained in the "string"

10

len_trim(string) It returns an integer equal to the length of "string" (len(string)) minus the number of trailing blanks

11

repeat(string,ncopy) It returns a string with length equal to "ncopy" times the length of "string", and containing "ncopy" concatenated copies of "string"

Example 1

此示例显示了 index 函数的使用−

This example shows the use of the index function −

program testingChars
implicit none

   character (80) :: text
   integer :: i

   text = 'The intrinsic data type character stores characters and   strings.'
   i=index(text,'character')

   if (i /= 0) then
      print *, ' The word character found at position ',i
      print *, ' in text: ', text
   end if

end program testingChars

当您编译并执行以上程序时，将生成以下结果——

When you compile and execute the above program it produces the following result −

The word character found at position 25
in text : The intrinsic data type character stores characters and strings.

Example 2

此示例演示了 trim 函数的使用−

This example demonstrates the use of the trim function −

program hello
implicit none

   character(len = 15) :: surname, firstname
   character(len = 6) :: title
   character(len = 25)::greetings

   title = 'Mr.'
   firstname = 'Rowan'
   surname = 'Atkinson'

   print *, 'Here is', title, firstname, surname
   print *, 'Here is', trim(title),' ',trim(firstname),' ', trim(surname)

end program hello

当您编译并执行以上程序时，将生成以下结果——

When you compile and execute the above program it produces the following result −

 Here isMr.   Rowan          Atkinson
 Here isMr. Rowan Atkinson

Example 3

此示例演示了 achar 函数的使用−

This example demonstrates the use of achar function −

program testingChars
implicit none

   character:: ch
   integer:: i

   do i = 65, 90
      ch = achar(i)
      print*, i, ' ', ch
   end do

end program testingChars

当您编译并执行以上程序时，将生成以下结果——

When you compile and execute the above program it produces the following result −

65  A
66  B
67  C
68  D
69  E
70  F
71  G
72  H
73  I
74  J
75  K
76  L
77  M
78  N
79  O
80  P
81  Q
82  R
83  S
84  T
85  U
86  V
87  W
88  X
89  Y
90  Z

Checking Lexical Order of Characters

以下函数确定字符的词法序列−

The following functions determine the lexical sequence of characters −

Sr.No

Function & Description

1

lle(char, char) Compares whether the first character is lexically less than or equal to the second

2

lge(char, char) Compares whether the first character is lexically greater than or equal to the second

3

lgt(char, char) Compares whether the first character is lexically greater than the second

4

llt(char, char) Compares whether the first character is lexically less than the second

Example 4

Example 4

以下函数演示如何使用 −

The following function demonstrates the use −

program testingChars
implicit none

   character:: a, b, c
   a = 'A'
   b = 'a'
   c = 'B'

   if(lgt(a,b)) then
      print *, 'A is lexically greater than a'
   else
      print *, 'a is lexically greater than A'
   end if

   if(lgt(a,c)) then
      print *, 'A is lexically greater than B'
   else
      print *, 'B is lexically greater than A'
   end if

   if(llt(a,b)) then
      print *, 'A is lexically less than a'
   end if

   if(llt(a,c)) then
      print *, 'A is lexically less than B'
   end if

end program testingChars

当您编译并执行以上程序时，将生成以下结果——

When you compile and execute the above program it produces the following result −

a is lexically greater than A
B is lexically greater than A
A is lexically less than a
A is lexically less than B