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| Author |
Problem with file input within nested loops
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| Army1987 2008-03-14, 7:32 pm |
| I have the following program:
PROGRAM read_matrix
IMPLICIT NONE
INTEGER i, j
REAL*8 matrix(4, 4)
OPEN(8, FILE='matrix.txt', STATUS='old', FORM='formatted')
DO i = 1, 4
READ(8, *) (matrix(i, j), j = 1, 4)
ENDDO
! Just an example:
WRITE(*, *) 'Matrix:'
DO i = 1, 4
WRITE(*, *) (matrix(i, j), j = 1, 4)
ENDDO
STOP
END
And it works (matrix.txt contains a 4x4 matrix, of course). Now if I make
it:
PROGRAM read_matrix
IMPLICIT NONE
INTEGER i, j
REAL*8 matrix(4, 4)
OPEN(8, FILE='matrix.txt', STATUS='old', FORM='formatted')
DO i = 1, 4
DO j = 1, 4
READ(8, *) matrix(i, j)
ENDDO
ENDDO
WRITE(*, *) 'Matrix:'
DO i = 1, 4
DO j = 1, 4
WRITE(*, *) matrix(i, j)
ENDDO
ENDDO
STOP
END
I get an end-of-file error. I didn't modify matrix.txt meanwhile. What is
wrong with the second program?
--
Armando di Matteo <a r m y one nine eight seven at e m a i l dot i t>
http://army1987.890m.org/
[Insert beautiful quotation here]
| |
| Arjen Markus 2008-03-14, 7:32 pm |
| On 14 mrt, 16:10, Army1987 <army1...@NOSPAM.it> wrote:
> I have the following program:
> =A0 =A0 =A0 PROGRAM read_matrix
> =A0 =A0 =A0 =A0 =A0IMPLICIT NONE
> =A0 =A0 =A0 =A0 =A0INTEGER i, j
> =A0 =A0 =A0 =A0 =A0REAL*8 matrix(4, 4)
>
> =A0 =A0 =A0 =A0 =A0OPEN(8, FILE=3D'matrix.txt', STATUS=3D'old', FORM=3D'fo=
rmatted')
> =A0 =A0 =A0 =A0 =A0DO i =3D 1, 4
> =A0 =A0 =A0 =A0 =A0 =A0 READ(8, *) (matrix(i, j), j =3D 1, 4)
> =A0 =A0 =A0 =A0 =A0ENDDO
> ! Just an example:
> =A0 =A0 =A0 =A0 =A0WRITE(*, *) 'Matrix:'
> =A0 =A0 =A0 =A0 =A0DO i =3D 1, 4
> =A0 =A0 =A0 =A0 =A0 =A0 WRITE(*, *) (matrix(i, j), j =3D 1, 4)
> =A0 =A0 =A0 =A0 =A0ENDDO
> =A0 =A0 =A0 =A0 =A0STOP
> =A0 =A0 =A0 END
> And it works (matrix.txt contains a 4x4 matrix, of course). Now if I make
> it:
> =A0 =A0 =A0 PROGRAM read_matrix
> =A0 =A0 =A0 =A0 =A0IMPLICIT NONE
> =A0 =A0 =A0 =A0 =A0INTEGER i, j
> =A0 =A0 =A0 =A0 =A0REAL*8 matrix(4, 4)
>
> =A0 =A0 =A0 =A0 =A0OPEN(8, FILE=3D'matrix.txt', STATUS=3D'old', FORM=3D'fo=
rmatted')
> =A0 =A0 =A0 =A0 =A0DO i =3D 1, 4
> =A0 =A0 =A0 =A0 =A0 =A0 DO j =3D 1, 4
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0READ(8, *) matrix(i, j)
> =A0 =A0 =A0 =A0 =A0 =A0 ENDDO
> =A0 =A0 =A0 =A0 =A0ENDDO
> =A0 =A0 =A0 =A0 =A0WRITE(*, *) 'Matrix:'
> =A0 =A0 =A0 =A0 =A0DO i =3D 1, 4
> =A0 =A0 =A0 =A0 =A0 =A0 DO j =3D 1, 4
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0WRITE(*, *) matrix(i, j)
> =A0 =A0 =A0 =A0 =A0 =A0 ENDDO
> =A0 =A0 =A0 =A0 =A0ENDDO
> =A0 =A0 =A0 =A0 =A0STOP
> =A0 =A0 =A0 END
> I get an end-of-file error. I didn't modify matrix.txt meanwhile. What is
> wrong with the second program?
>
> --
> Armando di Matteo <a r m y one nine eight seven at e m a i l dot i t>http:=
//army1987.890m.org/
> [Insert beautiful quotation here]
Each read in the two programs consumes an entire line. So, in the
first
case you read 4 lines and that is exactly what is in the file. In the
second case you try to read 16 lines (one number per read). And that
does not work.
Regards,
Arjen
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| Army1987 2008-03-14, 7:32 pm |
| Arjen Markus wrote:
> Each read in the two programs consumes an entire line. So, in the
> first
> case you read 4 lines and that is exactly what is in the file. In the
> second case you try to read 16 lines (one number per read). And that
> does not work.
I get it now: one read statement, one line, much like with write
statements, right?
--
Armando di Matteo <a r m y one nine eight seven at e m a i l dot i t>
http://army1987.890m.org/
[Insert beautiful quotation here]
| |
| glen herrmannsfeldt 2008-03-14, 7:32 pm |
| Army1987 wrote:
> Arjen Markus wrote:
[color=darkred]
> I get it now: one read statement, one line, much like
> with write statements, right?
Well, one or more whole lines in both cases.
If you have four values per line and read in five with
one READ statement, it will use two lines and ignore the
rest on the second line.
-- glen
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