Re: Parsing an empty member into a fusion adapted struct

On 05-05-17 19:54, Thomas Ellis wrote:
> I am currently working on developing a parse grammar which would allow me to handle the two input lines identified below with a single parse grammar.  The first input parses fine.  It is when there is nothing for that "field" where the difficulty lies.  Does anyone have any words of wisdom on how I might accomplish this?

The inputs strongly suggest that the format is fixed-width (and space
separated). So you would probably do best to parse it as such.

If you don't want to, and the trailing `request` value is mandatory, you
could look-ahead to assert that you're not able to parse the trailing
ushort_:

        linestruct = 
            ushort_ >> '-' >> ushort_ >> '-' >> ushort_ >>
            ushort_ >> ':' >> ushort_ >> ':' >> ushort_ >>
            -(~(ushort_ >> eoi) >> lexeme[ *alnum ]) >>
            -(~(ushort_ >> eoi) >> lexeme[ *alnum ]) >>
            ushort_;

Which _does_ work: http://coliru.stacked-crooked.com/a/53479b03385ca51d,
printing

<linestruct>

  <try>2017-04-18 23:59:55 </try>

  <success></success>

  <attributes>[[2017, 4, 18, 23, 59, 55, [h, p, c, h, l, p, 2, 0, 0], [6, Z, L, A], 9]]</attributes>

</linestruct>

Parse success

<linestruct>

  <try>2017-04-18 23:59:55 </try>

  <success></success>

  <attributes>[[2017, 4, 18, 23, 59, 55, [h, p, c, h, l, p, 2, 0, 0], [], 9]]</attributes>

</linestruct>

Parse success

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