Syntax error compiling old Fortran code

Question

I'm trying to compile legacy Fortran code with fort77. The command:

fort77 -c leg_code.f leg_code.o

fails with:

Error on line XXX: syntax error

Line XXX reads:

CHARACTER(LEN=10) TREE(2,MAXF)

where MAXF is defined some lines above with:

  INTEGER MAXF, MAXC
  PARAMETER (MAXF=400, MAXC=20)

If I remove (LEN=10), the code compiles with no issues.

Anyone know the reason for this error?

simply try :character(10) tree(2,maxf) or compile with a more modern fortran compiler (>= f90) — Francois Jacq
– Francois Jacq, Commented Dec 19, 2017 at 20:14
It looks like your code is at lesst Fortran 90 and you are using a Fortran 77 compiler. — Vladimir F Героям слава
– Vladimir F Героям слава, Commented Dec 19, 2017 at 20:25
It was a rather old code, so I thought I should compile with that. Didn't think if trying a more modern compiler. I tried with gfortran and it worked with no issues. Could either of you turn your comment into an answer so I can accept it? Thank you both! — Gabriel
– Gabriel, Commented Dec 19, 2017 at 20:41

francescalus · Accepted Answer · 2017-12-19 21:01:31Z

2

As noted in the comments, the declaration statement

CHARACTER(LEN=10) TREE(2,MAXF)

is not valid in Fortran 77. This form, declaring a rank-2 array of character of length 10, was introduced to standard Fortran in the Fortran 90 revision.

To declare such a variable in Fortran 77 the alternative form

CHARACTER*10 TREE(2,MAXF)

or

CHARACTER TREE(2,MAXF)*10

would be required. Simply removing the (len=10), as in

CHARACTER TREE(2,MAXF)

declares the variable to be an array of character of length 1, but this is valid in Fortran 77.

answered Dec 19, 2017 at 21:01

francescalus

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2 Comments

aka.nice Over a year ago

I don't remember being exposed to variant CHARACTER TREE*10 before, nice to still learn something about f77

francescalus Over a year ago

@aka.nice, the form character x*10 is still in modern Fortran. Indeed, it's still useful: it's the only way to override a character length declaration such as in character(len=27) x, y*10, z (much as one would see for overriding array size declarations integer, dimension(12) :: a, b(5), c).

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