On 12/27/18 11:08 PM, Henri Menke wrote:
On 12/27/18 10:43 PM, Floris van Manen wrote:
When trying to typeset, luatex kept complaining about incorrect parameters for ‘minus’. There is no \minus command in the source however. So it turns out that the combination of using \quad with ‘plus’, 'minus', and some more make the error appear. If i rewrite minus by {minus} the error does not show up either.
That's because the skips in spac-hor.mkiv are defined like this
\unexpanded\def\enskip{\hskip.5\emwidth} \unexpanded\def\quad {\hskip \emwidth} \unexpanded\def\qquad {\hskip 2\emwidth}
The syntax for the \hskip primitive is
\hskip<glue>
and the definition of <glue> is
<dimen>plus<dimen>minus<dimen>
So “\quad minuskel” will expand to “\hskip\emwidth minuskel”. You see what's going to happen? The “minus” will be interpreted as part of the glue definition but no <dimen> is following it, so you get an error. To fix the bug, the definitions in spac-hor.mkiv have to changed
\unexpanded\def\enskip{\hskip.5\emwidth\relax} \unexpanded\def\quad {\hskip \emwidth\relax} \unexpanded\def\qquad {\hskip 2\emwidth\relax}
As a temporary workaround you can also just copy them into your document.
There is even a comment in the TeXbook about this exact issue. \danger Horizontal glue is created in the same way, but with ^|\hskip| instead of\/ ^|\vskip|. For example, plain \TeX\ defines ^|\enskip| as an abbreviation for the command `|\hskip.5em\relax|'; this skips horizontally by one ``^{en},'' i.e., by exactly half of an em in the current font. There is no stretching or shrinking in an |\enskip|. The control sequence ^|\relax| after `|.5em|' prevents \TeX\ from thinking that a ^{keyword} is present, in case the text following |\enskip| just happens to begin with `|plus|' or `|minus|'.
\starttext \quad minuskel \stoptext
Where do i go wrong?
Thanks. Floris
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