[GRASS-dev] Fwd: Re: [GRASS-user] scientific notation

[Martin Landa]

Hi,

2007/11/25, Hamish <hamish_nospam at yahoo.com>:
> Fwd from Ivan, I wonder how G_scan_easting() and G_scan_northing() fit into

I do not fully understand this notation

> this problem? (for 1.2345e6 not 123:45:54.321E;  31E needs to be considered
> East)

anyway

$ cat pok.txt
123:45:54.321E|80N
1.2376508917e2|80N

$ v.in.ascii in=pok.txt out=pok

$ v.out.ascii pok
123.76508917|80|1
123.76508917|80|2

works for me...

Martin

> --Hamish
>
>
> Note: forwarded message attached.
>
>
>
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> ---------- Messaggio inoltrato ----------
> From: Ivan Shmakov <ivan at theory.asu.ru>
> To: Hamish <hamish_nospam at yahoo.com>
> Date: Sun, 25 Nov 2007 15:36:50 +0600
> Subject: Re: [GRASS-user] scientific notation
> [...]
>
>  >> Can GRASS actualy deal with number written with scientific notation ?
>  >> Is there a specific way to deal with these numbers ?
>
>  > v.in.ascii coulumn scanning code seems to overlook that case.
>
> [...]
>
>         Since my message has apparently not reached grass-dev, and since
>         you're interested in this problem, I'm forwarding it to you.
>         The problem seems to me somewhat trivial to solve.
>
>
>
> ---------- Messaggio inoltrato ----------
> From: Ivan Shmakov <ivan at theory.asu.ru>
> To: Martin Landa <landa.martin at gmail.com>
> Date: Sat, 24 Nov 2007 22:35:48 +0600
> Subject: Re: scientific notation
> >>>>> Martin Landa <landa.martin at gmail.com> writes:
>
> [...]
>
>  >> I would like to import points data in GRASS (with v.in.ascii).  My
>  >> data includes number written with the scientific notation (for
>  >> example 1.2e+23).  During the import, I am defining them as double.
>  >> Unfortunately, it doesn't work...
>
>  >> I get the following message :
>  >> " ERROR: Column 9 defined as double has string values "
>
>  >> Can GRASS actualy deal with number written with scientific notation ?
>  >> Is there a specific way to deal with these numbers ?
>
>  > no, it seems, v.in.ascii doesn't support it...
>
>         It seems that it's the is_double () function which behaves in a
>         wrong way:
>
> $ nl -ba grass-6.3.cvs_src_snapshot_2007_11_03/vector/v.in.ascii/points.c
> ...
>     30  /* Determine if the string is double, e.g. 123.456, +123.456, -123.456
>     31   * return 1 if double, 0 otherwise */
>     32  static int is_double(char *str)
>     33  {
>     34      int i = -1, ndots = 0;
>     35
>     36      while (str[++i] != '\0') {
>     37          if (i == 0 && (str[i] == '+' || str[i] == '-'))
>     38              continue;
>     39
>     40          if (str[i] == '.') {
>     41              if (ndots > 0)
>     42                  return 0;       /* > 1 dot */
>     43
>     44              ndots++;
>     45              continue;
>     46          }
>     47
>     48          if (!isdigit(str[i]))
>     49              return 0;
>     50      }
>     51
>     52      return 1;
>     53  }
> ...
> $
>
>
>         IIUC, the number is to be converted from its string
>         representation by atof () later.  Since, I assume, atof ()
>         supports e-notation, there's no necessity in such a strict check
>         like is_double () currently performs.  Therefore, I suggest
>         is_double () to be reimplemented on top of strtod () instead,
>         e. g.:
>
> static int
> is_double (char *s)
> {
>   char *tail;
>
>   if (strtod (s, &tail),
>       tail == s || *tail != '\0') {
>     /* doesn't look like a number,
>        or has extra characters after what looks to be a number */
>     return 0;
>   }
>
>   return 1;
> }
>
>         BTW, is_int () could be rewritten as well.
>
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-- 
Martin Landa <landa.martin at gmail.com> * http://gama.fsv.cvut.cz/~landa *