[Lemon-devel] [Lemon-user] GraphReader

[Alpár Jüttner]

Hi,

This design has much more drawbacks than advantages.

The worst thing is that it makes it fully impossible to write any tool
that would manipulate a general .lgf file. For example it is even
impossible to correctly read a general .lgf file into a graph editor.

Do we really need such a free file-format? Probably we don't.

I think we should insist on the original definition, i.e. the edgeset
and the nodeset of the file should consist of plain whitespace separated
columns. The only exception I would allow is that a column can also be a
string enclosed by two double-quotes characters (in order to enable
whitespace containing strings). Of course, we may also use a more
complex evaluation similar to the way the unix shells evaluate their
parameters, but I'm not sure if it is worth doing that.
This approach would make it possible to write general .lgf manipulation
tools, and it would also enable a much simpler API for making custom
readers/writers for special data types, as they would basically be
converters between std::string and the data type.

Of course, it also means that we must write e.g. "x + y / 82" instead of
just x + y / 82.
I think it is really worth doing that.

Regards,
Alpar



On Fri, 2008-01-18 at 17:20 +0100, Balazs Dezso wrote:
> Hi
> 
> > What is the reason for that?
> The reader does not cache the string representation of the map value, because 
> the map reader reads the value directly from the input stream. More general 
> reason, the graph IO design is based on the next rule, just the map knows 
> where is the end of its input. By example, the value may contains space, or 
> it should be well formed expression.
> 
> By example, valid values for some readers:
> Hello\ world!
> <xml> AB <tag> C </tag> D </xml>
> x + y / 82
> separator;
> "\"Hello\" \"World\""
> 
> Best, Balazs
> 
> On Friday 18 January 2008 16.50.25 you wrote:
> > Hi,
> >
> > > It is not possible, but an exception is thrown when you try to do this.
> >
> > What is the reason for that?
> >
> > >  The
> > > only solution is using maps such ForkWriteMap...
> > >
> > > Best, Balazs
> > >
> > > On Thursday 17 January 2008 11.07.26 Alpár Jüttner wrote:
> > > > Hi,
> > > >
> > > > Is it possible to read a column of an .lfg file into two different maps
> > > > (of different types, such as NodeMap<double> and NodeMap<std::string>)
> > > > at the same time?
> > > >
> > > > Regards,
> > > > Alpar
> > > >
> > > >
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>