[tex-k] Fwd: TeX

Jonathan Kew jfkthame at gmail.com
Tue Mar 15 16:43:19 CET 2022

On 15/03/2022 15:06, Ramtin Cabli wrote:
> /*Hi Master Knuth,*/
> /*
> */
> /*I have a point about plaintex (maybe a bug).*/
> /**/
> /*please look at this source:*/
> image.png
> /*there's no space between the third and fourth 'a' while after 
> \spacefactor there is space; the spaces after \spacefactor haven't been 
> seen by TeX.*/

The spaces after


simply terminate the number.

The definition of <normal integer> on page 269 of The TeXbook indicates 
that after an <integer constant> (sequence of digits), there may be <one 
optional space>.

So the space that terminates the number is absorbed as part of parsing 
the number, and does not contribute glue to the current list.

Adding more (literal) space characters makes no difference, because (as 
noted on page 37) "two spaces in a row count as one space".

> /*Therefore, I used two \space (not even one) immediately after 
> \spacefactor to get the desired space.*/

This is correct, because the <space> token generated by the first \space 
is absorbed during parsing of the number; then the second \space 
contributes to the current list.

So there's no bug here; this is behaving exactly as intended.


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