[XeTeX] not enough \XeTeXcharclass registers
Philip Taylor
P.Taylor at Rhul.Ac.Uk
Mon Feb 1 12:57:05 CET 2016
Jonathan Kew wrote:
> What happens at the boundary in "AB"? Should it depend on the numerical
> values of the classes, or the order in which the transitions were
> specified, or what?
"Clearly" it should not depend on the numerical values of the classes,
since in reality the precedence may have only a partial ordering :
(1 > 2 > 3 > 1)
but the use of a comma does not suggest ordering. Therefore I would
suggest a variant syntax :
\XeTeXintercharclasses `A = {1; 2}
\XeTeXintercharclasses `B = {3; 4}
where the semi-colon is an Algol-68 GOON (= "go on") delimiter
indication serial elaboration rather than collateral.
Given the modified syntax proposed above, what happens at the boundary
in "AB" would appear to me to be as follows :
[1] \XeTeXintercharclasses `A = {1; 2}
[1] \XeTeXintercharclasses `B = {3; 4}
[2] \XeTeXinterchartoks 1 3 = {foo}
[2] \XeTeXinterchartoks 1 4 = {bar}
[2] \XeTeXinterchartoks 2 3 = {xyzzy}
[2] \XeTeXinterchartoks 2 4 = {plugh}
Ruleset [1] states that 1-transitions are to be considered before
2-transitions when an "A" is encountered; similarly, the same ruleset
states that 3-transitions are to be considered before 4-transitions when
an "B" is encountered. Thus when we hit an "AB" sequence, the
interchartoks will be inserted in the order {foo}{bar}{xyzzy}{plugh}.
N'est-ce pas ?
Philip Taylor
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