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Re: [Groff] eqn: sqrt problems

From: Denis M. Wilson
Subject: Re: [Groff] eqn: sqrt problems
Date: Wed, 7 Sep 2011 15:19:49 +0100

On Tuesday 06 Sep 2011 14:48 Deri James wrote:

> On Friday 02 Sep 2011 12:22:46 Denis M. Wilson wrote:
> > Hello all,
> > 
> > There have been various postings on this list about the wrong
> > positioning of the radical extender. I found that it depended on
> > which font family was being used.  It turned out that some text
> > faces have a square root sign which was therefore being used in
> > place of that from the symbol font, but the extender was still from
> > symbol.
> > 
> > On removing them from the text fonts, the problem was cured.
> > 
> > So (a) when using a different family use a matching symbol face, or
> > (b) maths symbols should be omitted from text faces, or (c) eqn
> > should ensure that maths symbols are from the symbol fonts, or ...
> > 
> > What do people think?
> > 
> > Denis
> Denis,
> If the chosen font (which contains a radical) also contains a
> matching radicalex, the problem should not exist, since groff would
> choose the pair from the same font. The problem exists if only one of
> the pair of glyphs is available in the chosen fontNimbus Roman No9 L
> Regular Italic, the missing glyph will then be found in the Symbol
> font.
> The example below is using a font called U-TI which contains a
> radical glyph but no radicalex. The .char request specifies to groff
> to use the radical glyph from the Symbol font always .


Am I right in thinking your font U-TI is the URW Nimbus Roman No9 L
Regular Italic?  If so then its sqrt matches that from the Symbol font
S (if also URW), so a redefinition of sqrt is not necessary.

Different families from the URW set and others, however, show various
degrees of misalignment.  Using your clever trick. which I would modify

    .char \[sqrt] \f[S]\[sqrt]\f[]

the misalignment was *reduced* but not removed.  If I added

    .char \[sr] \f[S]\[sr]\f[]

Then everything comes out perfectly, which is very mysterious, as gnu
eqn does *not* use \[sr].  But it also comes out correctly to use

    .char \[sqrt] \f[S]\[sr]\f[]

I've come round to thinking this is a weakness in eqn, and that my
solution (c) may be the proper one, as there may be other maths symbols
in some text fonts that are also in Symbol, causing unexpected errors
(proof needed).


> .char \[sqrt] \f[S]\[sqrt]\fP
> .EQ
> gfont U-TI
> 1 over sqrt {ax sup 2 +bx+c}
> .EN
> Someone else may have a more elegant solution.
> Cheers 
> Deri

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