Re: smb.time || smb2.time is valid in a filter string but not in a custom column field?

[Jeff Morriss <jeff.morriss.ws () gmail com>]

On 06/13/13 20:46, Guy Harris wrote:
> On Jun 13, 2013, at 5:16 PM, Richard Sharpe <realrichardsharpe () gmail com> wrote:
>
> > I thought I would try to work around my issue with smb.time vs
> > smb2.time by using a custom column field and putting in an expression,
> > but it seems not to work. An expression that is acceptable in the
> > Filter field is not acceptable in a custom column.
> >
> > Why is this?
>
> Because "||" is a Boolean "or", not a human-language "or". :-)
>
> I.e., "a || b" is a packet-matching expression that matches if the expression "a" matches or the expression "b" matches, not a field expression that 
> evaluates to whichever of the fields "a" or "b" is present (with "a" chosen if both are present, presumably).
>
> The Filter field takes packet-matching expressions; the custom column field takes field names.  Field names are valid packet-matching 
> expressions, which match if the field is present in the packet and don't match if it's not, but arbitrary packet-matching 
> expressions aren't valid as custom columns.
>
> Having a separate feature allowing a set of field names for a custom column could be useful.  I'm not sure an "||" 
> operator, given its existing meaning in C (and in packet-matching expressions), would be the right syntax for that.

What would an "or" in the context of columns mean?  In particular in the 
case where both fields have a value.

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