Subject: Re: fences (variable size math symbols) From: David Carlisle <davidc@xxxxxxxxx> Date: Tue, 9 Jun 1998 09:46:46 +0100 
Gregg, Thanks for the comments. I will experiment some more before coming back. While I know something about TeX I am still basically teaching myself dsssl, so sometimes I am not clear in my own mind whether things I am finding difficult are because they are difficult or because I have not mastered the appropriate bit of dsssl yet. So I don't want to abuse this list too often. > but do you recall what fun it was to learn TeX? Just about, but I'm getting too old to remember my youth. > Can you post an example of the source text upon which you expect > to operate along with a description of what the expected output would > be? Will try below, although I came to this question by contemplating how to implement the mathml report rather than by having a particular example. > One specific point, though: I suspect issues like the exact sizing > of the fences as you mention above are what the standard has in mind in > note 122 wrt implementation dependencies. Also, have you looked at how > a math grid flow object might be used for this? Yes fence stretching is explicitly implementation dependent. But that is why I can not see how to do multiple fences with the current `two fence' flow object. To use TeX syntax for a moment... If I want to produce ( a + b ) + ( c + d ) with all the brackets the same size (and `a' `b' etc something large enough that this is an issue). Then in MathML I am just supposed to put all 11 elements in a <mrow> and give the brackets fence="true" and stretchy="true" attributes (which actually they have by default.) Then TeX does not support this at all easily (and dsssl likewise). You could try to arbitrarily nest, something like <null><null>( a + b ) + ( c + d )   _______    _______________  _____________________________ but that gets the horizontal spacing wrong (which could be corrected), inhibits line breaking (could possibly be corrected, but I don't think I can do anything about that from within dsssl) and most importantly I need to know what the `system dependent' stretching is doing. If the brackets around (a+b) mean that the resulting expression is larger than a+b then the above nested form will make the second and third brackets progressively larger. That is, if my system dependent part is doing what the second TeX expression below is doing, then I need to know not to try to use nested fence objects in dsssl. =================== plain tex example. $\left.\left.\left( a + b \right) + \right( c + d \right)$ \delimitershortfall0pt \delimiterfactor1002 $\left.\left.\left( a + b \right) + \right( c + d \right)$ \bye =================== > The presentation elements are meant to > express the syntactic structure of math notation in much the same way as > titles, sections, and paragraphs capture the higher level syntactic > structure of a textual document." We may not have quite the same > latitude for formatting the former as for the latter, but the > structure/format distinction is still there. Actually one of my gripes about the MathML report is that it over specifies the formatting. In particular the spacing around operators are fixed (to often inappropriate values) You can override with attributes in the document markup but that is not really what I want to see. Of course MathML also has hooks for giving semanticonly information without explicit presentational style at all. In particular it mentions OpenMath at several points as a suitable language. Which is the project that I am currently working on. http://www.nag.co.uk/projects/OpenMath.html > Excellent! Something that will work with JadeTex? Are you > doing all the math stuff in DSSSL? Etc, etc. More info! Well my dsssl is not yet for public consumption. (and anyway it doesn't yet work) as I have mainly been trying to map in my own mind how to understand the hard bits like fences and alignments. I still have to do the useful but dull work of mapping all the mathml operators numbers etc to suitable dsssl. jade/jadetex is what I am using initially but I'd hope to keep to standard dsssl constructions so that the thing would work with any dsssl system. This format neutral style specification is presumably the main advantage of dsssl (otherwise I could more easily just get TeX to read the MathML files directly). David DSSSList info and archive: http://www.mulberrytech.com/dsssl/dssslist
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