75 lines
2.1 KiB
Fortran
75 lines
2.1 KiB
Fortran
!Implemented by Anant Dixit (October, 2014)
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program animated_pendulum
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implicit none
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double precision, parameter :: pi = 4.0D0*atan(1.0D0), l = 1.0D-1, dt = 1.0D-2, g = 9.8D0
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integer :: io
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double precision :: s_ang, c_ang, p_ang, n_ang
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write(*,*) 'Enter starting angle (in degrees):'
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do
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read(*,*,iostat=io) s_ang
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if(io.ne.0 .or. s_ang.lt.-90.0D0 .or. s_ang.gt.90.0D0) then
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write(*,*) 'Please enter an angle between 90 and -90 degrees:'
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else
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exit
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end if
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end do
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call execute_command_line('cls')
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c_ang = s_ang*pi/180.0D0
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p_ang = c_ang
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call display(c_ang)
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do
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call next_time_step(c_ang,p_ang,g,l,dt,n_ang)
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if(abs(c_ang-p_ang).ge.0.05D0) then
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call execute_command_line('cls')
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call display(c_ang)
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end if
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end do
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end program
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subroutine next_time_step(c_ang,p_ang,g,l,dt,n_ang)
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double precision :: c_ang, p_ang, g, l, dt, n_ang
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n_ang = (-g*sin(c_ang)/l)*2.0D0*dt**2 + 2.0D0*c_ang - p_ang
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p_ang = c_ang
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c_ang = n_ang
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end subroutine
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subroutine display(c_ang)
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double precision :: c_ang
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character (len=*), parameter :: cfmt = '(A1)'
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double precision :: rx, ry
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integer :: x, y, i, j
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rx = 45.0D0*sin(c_ang)
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ry = 22.5D0*cos(c_ang)
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x = int(rx)+51
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y = int(ry)+2
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do i = 1,32
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do j = 1,100
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if(i.eq.y .and. j.eq.x) then
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write(*,cfmt,advance='no') 'O'
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else if(i.eq.y .and. (j.eq.(x-1).or.j.eq.(x+1))) then
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write(*,cfmt,advance='no') 'G'
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else if(j.eq.x .and. (i.eq.(y-1).or.i.eq.(y+1))) then
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write(*,cfmt,advance='no') 'G'
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else if(i.eq.y .and. (j.eq.(x-2).or.j.eq.(x+2))) then
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write(*,cfmt,advance='no') '#'
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else if(j.eq.x .and. (i.eq.(y-2).or.i.eq.(y+2))) then
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write(*,cfmt,advance='no') 'G'
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else if((i.eq.(y+1).and.j.eq.(x+1)) .or. (i.eq.(y-1).and.j.eq.(x-1))) then
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write(*,cfmt,advance='no') '#'
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else if((i.eq.(y+1).and.j.eq.(x-1)) .or. (i.eq.(y-1).and.j.eq.(x+1))) then
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write(*,cfmt,advance='no') '#'
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else if(j.eq.50) then
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write(*,cfmt,advance='no') '|'
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else if(i.eq.2) then
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write(*,cfmt,advance='no') '-'
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else
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write(*,cfmt,advance='no') ' '
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end if
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end do
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write(*,*)
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end do
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end subroutine
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