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From: John E. Potter (jpotter_at_[hidden])
Date: 2001-01-28 07:58:28

On Sun, 28 Jan 2001, David Abrahams wrote:

> ----- Original Message -----
> From: "John E. Potter" <jpotter_at_[hidden]>
> > Are bidirectional maps really dynamic?
> >
> > I leave the rest for consideration of the above. It may be the case
> > that bidirectional maps are only constructed and used.
> Bidirectional maps really are dynamic. I've given examples before of
> bidirectional maps which model monotonic piecewise linear functions (e.g.
> mapping between word index and layout position in a text document, or time
> and position in music, or time and word index in a speech transcription...)
> in the context of our discussion on heterogeneous comparison operators with
> the standard binary search functions. It's common to want to change these
> things dynamically. For example, as one is editing a document in a word
> processor, line breaks tend toward stability, so it's easy to imagine an
> application making dynamic modifications to small regions of such a map when
> appropriate.

These may be two different subjects. Consider six bit mime encoding. The
function is not monotonic piecewise linear, but it does have an inverse
and it is constant.

What are the uses of 1to1 maps? If they are usually static, the interface
would be nothing like a standard container. I wonder what George had
in mind when he started this thread.


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