[GRASS-user] distance from extent to origin cost surfaces

[Hamish]

> Dylan wrote:
> > I need a little help understanding this little bit from the original
> > code:
> > 
> > if (!G_is_d_null_value(c))
> >           {
> >            out_row[col] = opt.new->answer
> >                           ? newval
> >                           : *c;
> >            break;
> >           }
> > 
> > what exactly is this stanza doing, and why does it contain newval
> > *and* opt.new->answer ??
> 
Hamish:
> result = (if_this_is_true) ? then_set_result_to_this : otherwise_this
> 
> In this case it tests to see if the new= "new value" option was given,
> in the case of a flag this is directly true or false. In the case of an
> option= (as here), the test is to see if the answer is NULL, ie if the
> user used that option on the command line or not. If they didn't use it
> and it doesn't have a default answer, it will be NULL.
> 
> So this code tests to see if the new= option was given, and if it was
> it uses the value given for that option, otherwise it uses the value of
> the cell, which has just been confirmed as non-null.

.... and opt.new->answer is a string while newval is a number:

[earlier in the code]
        if (opt.new->answer)
                newval = atoi(opt.new->answer);



Hamish



     
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