Re: [bug-gawk] Can a key in a array be deleted while the array is iterated?

[Manuel Collado]

El 02/01/2017 4:19, Andrew J. Schorr escribió:
> On Sun, Jan 01, 2017 at 07:05:29PM -0600, Peng Yu wrote:
> > I made the following function to intersect the keys of x1 and x2. The
> > results is saved in x1. I am not sure it is OK to change an array
> > while it is being iterated. Will the function always work? Thanks.
> >
> > function arrkeyintersect(x1, x2,    k) {
> >      for(k in x1) {
> >          if(!(k in x2)) {
> >              delete x1[k]
> >          }
> >      }
> > }
>
> It is safe. This should be apparent from the documentation:
>     https://www.gnu.org/software/gawk/manual/html_node/Delete.html

Well, it seems safe to modify the current iterated array element. But 
modifying array elements other then the current one may be troublesome.

In this particular case, the original code could be modified by 
iterating over the second (unchanged) array instead of the first (been 
modified) one. As follows:

function arrkeyintersect(x1, x2,    k) {
    for(k in x2) {
        delete x1[k]
        }
    }
}

HTH.
--
Manuel Collado - http://lml.ls.fi.upm.es/~mcollado