Re: [vhdl-200x] Image attribute for array types

On Tue, 2014-07-22 at 21:48 -0700, Jim Lewis wrote:
> If we do not support arbitrary sized composites, then where do we stop?
> 
> Currently we stopped before we implemented write and to_string for
> integer_vector, real_vector, ...  I am really missing these.  So why
> not try to generalize a solution and allow overloading to clean up any
> issues introduced.
> 
> In 2008 we committed to the to_string route since it is overloaded.  It
> is too bad there are differences between 'image and to_string for
> character as otherwise, it would be interesting to merge the two and
> have 'image to implicitly call to_string (explicit version if it exists
> or otherwise the implicit one). Would it be horrible to have
> character'image('A') return a string containing A without the single
> quotes?

There is a precedent in Ada for attaching user-written functions to
implement attributes - but not specifically the 'image attribute,
through the syntax "for <type'attribute> use <function>". Then the
user-provided function replaces the default implementation.

Where this is used in Ada is with the stream I/O attributes 'read and
'write (ditto 'input and 'output) allowing you to stream arbitrary
objects to/from file, and to switch between different file formats by
evaluating the "for ... use" clauses. Can be a little tricky to set up
but works really well.

Then you could have character'image('A') work any way you want.

Caveat: I have not studied the details or looked at the AIs to see if
this was also considered for 'image and 'value, and (if so) what the
issues were, but I would be surprised if it hadn't been given some
consideration.

- Brian





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