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Fortran 90/95 メモ

Hello World

program hello
  implicit none
  print *, 'Hello World!'
end program hello

> gfortran hello.f90 -o hello
> ./hello
Hello World!

コメントアウト

• ! 1行コメント

データ型

real,parameter :: pi = 3.14
complex :: c = (7.0, 3.0)
character(len=7) :: n = '7mizuki'
data a,b/1,2/ c,d/2*0/ ! a=1, b=2, c=0, d=0

属性

• dimension 形状指定
• parameter 定数指定
• allocatable 動的領域確保
• optional 省略可能な引数
• intent(opt) 授受特性 opt: in, out, inout

文字列

• character a ! 長さ1
• character(len=7) b ! 長さ7
• character(7) c
• character*7 d
• character e*7, f*3

boolean

• .true.
• .false.

型変換

• int() ! real → int 切り捨て
• nint() ! real → int 四捨五入
• real() ! int → real
• dble() ! int → double precision

! int ⇒ character
character(3) a
integer :: i = 123
write (a,*) i

! character
character(3) a
integer i
a = "123"
read (a,*) i

配列

integer,dimension(7) :: a = 3
! a(1) = 3, a(2) = 3, ..., a(7) = 3

integer a(7)
data a/7*3/
! a(1) = 3, a(2) = 3, ..., a(7) = 3

integer :: b(3) = (/1, 2, 3/)
integer :: c(3) = (/(i*7, i=1,3)/) ! 1, 14, 21

integer :: d(2,3) = reshape((/i, i=1,6/), (/2,3/))
! 1 3 5
! 2 4 6

! 部分配列
integer e(7)
e(:) = 0
! 0 0 0 0 0 0 0

d(1:7:2) = 7
! 7 0 7 0 7 0 7

d(2:4) = 3
! 7 3 3 3 7 0 7

d(7:1:-1)
! 7 0 7 3 3 3 7

演算子

• + - * / ** //
• < > == /= <= >=
  .lt. .gt. .eq. .ne. .gt. .ge.
• .not. .and. .or. .eqv. .neqv.

制御

• continue
• cycle
• do
• exit
• go to
• if then [else if [else]]
• return
• select case [case default]
• stop

関数

program func
  print *, inc(1)
contains
  integer function inc(n)
    integer,intent(in) :: n
    inc = n + 1
  end function inc
end program func

組込み手続き

• sum
• minval
• maxval
• lbound
• ubound
• allocate
• deallocate
• len
• trim
• trim_len

時間

• system_clock
• cpu_time

integer t1, t2, t_rate, t_max, diff
call system_clock(t1)
  ! do something
call system_clock(t2, t_rate, t_max)
if ( t2 < t1 ) then
  diff = t_max - t1 + t2
else
  diff = t2 - t1
endif
print *, diff/dble(t_rate)

real t1, t2
call cpu_time( t1 )
  ! do something
call cpu_time( t2 )
print *, t2 - t1

リンク

• Fortran入門
• Wikipedia

コンパイラ

• The G95 Project
• GNU Fortran