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From: Maurizio Vitale (mav_at_[hidden])
Date: 2007-04-27 03:55:16

I think I haven't really understood how proto handles transforms and pattern matching.
I'm probably confused on how exactly result_of, arg and mpl placeholders play together
and I kind of get what I want in some cases.
For instance, given the pattern:

 proto::terminal< number<bounds<run_time,_>,_,_,_,_,_> >

how can I refer in the rhs of a transform to:

    a) the entire pattern being matched (e.g. terminal<> or number<>)
    b) the bound<> subobject
    c) the expression corresponding to the placeholder inside the bound object
    d) the expression corresponding to one of the other 5 placeholders in the number<> subtree

I'm particular unclear on how placeholders are bound to mpl placeholders: left to right,
depth/breath first traversal of the parse tree, some other way.

The only examples I've found uses mpl::_ and has a single proto::_ universal matcher in the
lhs so is not like I have any evidence of an intention to bind other mpl placeholders.
Maybe I have to dissect the matched expression myself, but I need at least to get an handle
to the entire expression.

This is blocking me at the moment, so if anybody has suggestions, they would be very much

Best regards,


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