Re: [Spirit-general] Omit unwanted spaces in karma::left_align

[Hartmut K. <har...@gm...>]

> the example attached works, but I like some cosmetic changes.
> 
> In the output of the 2nd row there are spaces generated if the trailing
> rule uvw doesn't generate any output. This I want to omitted, but how to?
> Any help is approbate :-)

The trailing spaces are generated by the left_align directive. That means in
order to avoid them you need to get rid of the alignment directive. You
could move the last left_align before uvw into a separate rule:

    new_r = left_align(40)[string] << uvw | string;

i.e. left align the first attribute if uvw succeeds, and print it verbatim
otherwise. But for this the first alternative needs to fail if it wouldn't
produce any output.

> BTW, is there a complement in karma to qi's on_error<> to catch generating
> errors on composite rules?

Not yet, mainly as nobody has asked for it. But, I was planning to add
similar functionality. 

Regards Hartmut

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