Converting integer to character in Fortran90

问题

I am trying to convert an integer to character in my program in Fortran 90. Here is my code:

Write(Array(i,j),'(I5)') Myarray(i,j)

Array is an integer array and Myarray is a character array, and '(I5)', I don't know what it is, just worked for me before!

Error is:

"Unit has neither been opened not preconnected"

and sometimes

"Format/data mismatch"!

回答1:

Alexander Vogt explains the meaning of the (I5) part. That answer also points out some other issues and fixes the main problem. It doesn't quite explicitly state the solution, so I'll write that here.

You have two errors, but both have the same cause. I'll re-state your write statement explicitly stating something which is implicit.

Write(unit=Array(i,j),'(I5)') Myarray(i,j)

That implicit thing is unit=. You are, then, asking to write the character variable Myarray(i,j) to the file connected to unit given by the integer variable Array(i,j).

For some values of the unit integer the file is not pre-connected. You may want to read about that. When it isn't you get the first error:

Unit has neither been opened not preconnected

For some values of Array(i,j), say 5, 6 or some other value depending on the compiler, the unit would be pre-connected. Then that first error doesn't come about and you get to

Format/data mismatch

because you are trying to write out a character variable with an integer edit descriptor.

This answer, then, is a long way of saying that you want to do

Write(Myarray(i,j),'(I5)') array(i,j)

You want to write the integer value to a character variable.

Finally, note that if you made the same mistake with a real variable array instead of integer, you would have got a different error message. In one way you just got unlucky that your syntax was correct but the intention was wrong.

回答2:

'(I5)' is the format specifier for the write statement: write the value as an integer with five characters in total.

Several thing could go wrong:

Make sure that Myarray really is an integer (and not e.g. a real)
Make sure array is a character array with a length of at least five characters for each element
Take care of the array shapes
Ensure that i and j hold valid values

Here is a working example:

program test
  implicit none
  character(len=5) :: array(2,2)
  integer,parameter :: myArray(2,2) = reshape([1, 2, 3, 4], [2, 2])
  integer           :: i, j

  do j=1,size(myArray,2)
    do i=1,size(myArray,1)
      write(array(i,j), '(I5)' ) myArray(i,j)
    enddo !i
  enddo !j

  print *, myArray(1,:)
  print *, myArray(2,:)
  print *,'--'
  print *, array(1,:)
  print *, array(2,:)
end program

来源：https://stackoverflow.com/questions/30643905/converting-integer-to-character-in-fortran90

标签

fortran

fortran90