Re: bijective (was re: An Absurdly Brief Introduction to Unicode (was Re:

From: Tom Lord (
Date: Sat Feb 24 2001 - 03:41:34 EST

        I think I'd like bijective too, if I knew what it meant. Someone?

It would be a lot more fun to answer this question in plain-text
Unicode (using math notation) than in ASCII.


"Bijective" describes a mapping between two sets. Every element of
the source set ("the domain") is mapped to a unique element of the
destination set ("the codomain") AND there are no left over elements
in the codomain. A one to one mapping. An invertible mapping.

"Injective" describes a mapping where every element of the domain maps
to a unique element, but there may be left over elements in the

So, if you have a legacy character set for which Unicode provides a
loss-less transcoding, then there is an injective mapping from that
legacy set to Unicode, and, equivalently, a bijective mapping from the
legacy set to a certain subset of Unicode.

In the revised version of the absurdly short introduction, I have
avoided the term "bijective".

This is now way off topic, so please think twice about following up.

Thomas Lord

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