CODEWITHSUNDEEP
arraysfortran
gugabrielle
gugabrielle

Reputation: 39

unknown wrong in a fortran array code

I checked this code many times and could not figure out how to correct it.

program main
implicit none

real, parameter :: dx=1
real, parameter :: dy=1

real :: a1, a2, a3, a4, a5
a1=dy/dx
a2=dx/dy
a3=-2*(dy/dx+dx/dy)
a4=dx/dy
a5=dy/dx

REAL, DIMENSION(5,1):: a
DATA a/a1,a2,a3,a4,a5/

!write (*,*) a(1),a(2)
pause
endprogram

thank you very much and the error:
error #6236:A specification statement cannot appear in the executable section. error #6404: This name does not have a type, and must have an explicit type. [A] error #6211: A symbol must be a defined parameter in this context.

Upvotes: 0

Views: 2249

Answers (1)

Vladimir F Героям слава
Vladimir F Героям слава

Reputation: 59998

You are mixing specification (data declaration) statements and executable statements. The declaration statements must go first and the executable statements can only follow after them inside each compilation unit or block.

Also, entity used for initialization in the DATA statement must be a constant expression.

One way to fix your code is:

program main
  implicit none

  real, parameter :: dx=1
  real, parameter :: dy=1

  real, parameter :: a1=dy/dx
  real, parameter :: a2=dx/dy
  real, parameter :: a3=-2*(dy/dx+dx/dy)
  real, parameter :: a4=dx/dy
  real, parameter :: a5=dy/dx

  REAL, DIMENSION(5,1):: a
  DATA a/a1,a2,a3,a4,a5/

  !write (*,*) a(1),a(2)

end program

Don't use the PAUSE statement. It is deleted from modern Fortran and it is not clear (portably) what should it actually do even in the older versions.

You can also initialize the array using an array constructor. You don't need constant expressions in that case:

program main
  implicit none

  real, parameter :: dx=1
  real, parameter :: dy=1
  REAL, DIMENSION(5,1) :: a

  a = reshape([dy/dx, dx/dy, -2*(dy/dx+dx/dy), dx/dy, dy/dx], [5,1])
end program

Upvotes: 2

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