- Fortran 教程
- Fortran - 首页
- Fortran - 概述
- Fortran - 环境设置
- Fortran - 基本语法
- Fortran - 数据类型
- Fortran - 变量
- Fortran - 常量
- Fortran - 运算符
- Fortran - 决策
- Fortran - 循环
- Fortran - 数字
- Fortran - 字符
- Fortran - 字符串
- Fortran - 数组
- Fortran - 动态数组
- Fortran - 派生数据类型
- Fortran - 指针
- Fortran - 基本输入输出
- Fortran - 文件输入输出
- Fortran - 过程
- Fortran - 模块
- Fortran - 内在函数
- Fortran - 数值精度
- Fortran - 程序库
- Fortran - 编程风格
- Fortran - 程序调试
- Fortran 资源
- Fortran - 快速指南
- Fortran - 有用资源
- Fortran - 讨论
Fortran - 动态数组
动态数组是指大小在编译时未知,而是在运行时才确定的数组。
动态数组用属性allocatable声明。
例如:
real, dimension (:,:), allocatable :: darray
数组的秩(即维度)必须声明,但是要为这样的数组分配内存,需要使用allocate函数。
allocate ( darray(s1,s2) )
数组在程序中使用完毕后,应该使用deallocate函数释放已分配的内存。
deallocate (darray)
示例
下面的例子演示了上面讨论的概念。
program dynamic_array implicit none !rank is 2, but size not known real, dimension (:,:), allocatable :: darray integer :: s1, s2 integer :: i, j print*, "Enter the size of the array:" read*, s1, s2 ! allocate memory allocate ( darray(s1,s2) ) do i = 1, s1 do j = 1, s2 darray(i,j) = i*j print*, "darray(",i,",",j,") = ", darray(i,j) end do end do deallocate (darray) end program dynamic_array
编译并运行上述代码后,将产生以下结果:
Enter the size of the array: 3,4 darray( 1 , 1 ) = 1.00000000 darray( 1 , 2 ) = 2.00000000 darray( 1 , 3 ) = 3.00000000 darray( 1 , 4 ) = 4.00000000 darray( 2 , 1 ) = 2.00000000 darray( 2 , 2 ) = 4.00000000 darray( 2 , 3 ) = 6.00000000 darray( 2 , 4 ) = 8.00000000 darray( 3 , 1 ) = 3.00000000 darray( 3 , 2 ) = 6.00000000 darray( 3 , 3 ) = 9.00000000 darray( 3 , 4 ) = 12.0000000
DATA语句的使用
data语句可以用来初始化多个数组,或进行数组段的初始化。
data语句的语法如下:
data variable / list / ...
示例
下面的例子演示了这个概念:
program dataStatement implicit none integer :: a(5), b(3,3), c(10),i, j data a /7,8,9,10,11/ data b(1,:) /1,1,1/ data b(2,:)/2,2,2/ data b(3,:)/3,3,3/ data (c(i),i = 1,10,2) /4,5,6,7,8/ data (c(i),i = 2,10,2)/5*2/ Print *, 'The A array:' do j = 1, 5 print*, a(j) end do Print *, 'The B array:' do i = lbound(b,1), ubound(b,1) write(*,*) (b(i,j), j = lbound(b,2), ubound(b,2)) end do Print *, 'The C array:' do j = 1, 10 print*, c(j) end do end program dataStatement
编译并运行上述代码后,将产生以下结果:
The A array: 7 8 9 10 11 The B array: 1 1 1 2 2 2 3 3 3 The C array: 4 2 5 2 6 2 7 2 8 2
WHERE语句的使用
where语句允许你根据某个逻辑条件的结果,在表达式中使用数组的某些元素。只有当给定的条件为真时,才对元素执行表达式。
示例
下面的例子演示了这个概念:
program whereStatement implicit none integer :: a(3,5), i , j do i = 1,3 do j = 1, 5 a(i,j) = j-i end do end do Print *, 'The A array:' do i = lbound(a,1), ubound(a,1) write(*,*) (a(i,j), j = lbound(a,2), ubound(a,2)) end do where( a<0 ) a = 1 elsewhere a = 5 end where Print *, 'The A array:' do i = lbound(a,1), ubound(a,1) write(*,*) (a(i,j), j = lbound(a,2), ubound(a,2)) end do end program whereStatement
编译并运行上述代码后,将产生以下结果:
The A array: 0 1 2 3 4 -1 0 1 2 3 -2 -1 0 1 2 The A array: 5 5 5 5 5 1 5 5 5 5 1 1 5 5 5
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