Defn. of Extender (Pdn. 89) again

Paul W. Abrahams abrahams at
Thu Aug 26 05:03:23 BST 1999

Steve Dahl wrote:

> My guess is that 0xB7 and 0x387 were included either by accident, or else in Unicode 1.0, they
> were incorrectly classified as Lm characters. I can't find my old Unicode 1.0 chart, so I
> don't know.
> My guess is that Extender character means a character classified as Lm. As far as I can tell,
> these are characters that make no sense unless they follow another letter. Think of them as
> being equivalent to diacritical marks, except that they take up space next to the modified
> character, whereas normal diacritical marks fit in the same visual character cell as the
> character they modify. The Lm character must always be displayed next to its preceding
> character, and it's illegal to break the line between an Lm character and its preceding
> character.

The trouble is that there are lots of other Lm characters  besides those classified as
extenders.  For example:

> 02B2;MODIFIER LETTER SMALL J;Lm;0;L;<super> 006A;;;;N;;;;;
> 02B3;MODIFIER LETTER SMALL R;Lm;0;L;<super> 0072;;;;N;;;;;

Why aren't those also considered to be extenders?  There seems to be some history and motivation
here that needs explaining.


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