ncgen don't line "minus zero".

• To: netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: ncgen don't line "minus zero".
• From: B.Bretthauer@xxxxxx (Bernward Bretthauer)
• Date: Mon, 13 Feb 1995 16:55:08 +0100

If a variable in an .cdl file contains a value of "-0" or "+0", ncgen 
produces a syntax error. The reason is seems to be the following in ncgen.l:
[+-]?[1-9][0-9]*[lL]?|0[lL]? {

I am not familar with lex, but it seems to me, the author defined a long
constant as beginning with + or - and a number 1-9, or as a single 0 without
+ or -.

I don't know why this was done, so I don't want to change it. 

The whole thing don't look like a problem, why should anyone insert a -0 in
his .cdl file?

BUT: At least on the Sun (SUN OS 4.1.3), ncdump often generates a -0!
(This seems to be a bug in SUNs output formatting routines, the MS-DOS Version
of ncdump don't have this problem).

Run the following little program:
/* ------------- Cut Here ----------------*/
#include <stdio.h>
#include <netcdf.h>

main()
{
  double d=0;
  int ncid, dimid, varid;
  long start=0, count=1;



  d *= -1;

  ncid = nccreate("test.nc",NC_CLOBBER);
  dimid=ncdimdef(ncid, "time",1);
  varid=ncvardef(ncid, "velocity",NC_DOUBLE,1,&dimid);
  ncendef(ncid);
  ncvarput (ncid,varid,&start, &count,&d);
  ncclose(ncid);
}
/* ------------- Cut Here ----------------*/
Now run "ncdump test.nc":

netcdf test {
dimensions:
        time = 1 ;

variables:
        double velocity(time) ;

data:

 velocity = -0 ;  // <---------- Here it is.
}

Try to run ncgen on the output and you get:
ncgen: test.cdl line 10: syntax error
 
Now I would like to change ncgen to accept the "-0" or ncdump to
produce at least "-0." like it does in attributes. Any ideas what's the
best solution?

Bernward Bretthauer
  
 


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