# change \sqrt symbol

I'm trying to change the sqrt sign into the glyph '317 of the following character map, that is the mathematical pi three font table.

I would use it only for non-large root, e.g \sqrt{a}, \sqrt{5/2} etc. So, I use this instruction

 \DeclareMathRadical{\sqrtsign}{mathpi3}{'317}{largesymbols}{"70}


where mathpi3 is the name of the alphabet that represents mathematical pi three font, and largesymbols the ordinary cmex font.

Actually, it does not work correctly because I think I need to change also the overline of the root (e.g. using '267 or '167 glyphs). In fact, the output of this instruction is posted in the following picture

In addition, I think I may change the encoding of the font, in order to put the glyph on the correct position into the font table (the "70 one), but actually I'm not able to do this.

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\DeclareMathRadical is a wrapper around the \radical TeX primitive and in classical TeX, that takes a character position for the sqrt sign and takes the rule thickness for the over bar from the height of that character. If you look at font tables for TeX fonts the sqrt sign character hangs almost entirely below the baseline so that the rule gets a reasonable thickness. The \radical primitive then raises it while typesetting.

This a major reason why TeX fonts are not easily usable by non-TeX systems and the other way round.

You could set up a virtual font in which this character is lowered (someone may have done that already, I'm not sure) but if it is just for occasional use for normal sized arguments it is simpler not to use the \radical mechanism at all, simply use the character as a normal character and use \overline over the argument with some spacing adjustments to make things line up.

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And is there a way to raise the frac line? I'm using the whole mathematical pi font volume and I have changed many symbols into the mathematical pi ones, for example those of binary operation and relations. Thus, I need to use its frac line (that belongs to mathematical pi 1) or raise the ordinary tex primitive in order to get the right height. –  Lorenzo Apr 22 '13 at 16:01
Another question: I have a lot of book typeset with mathematical pi font volume. May they be typeset using Quarkxpress or adobe indesign? I could post a pdf that shows what I mean –  Lorenzo Apr 22 '13 at 16:06
@Lorenzo TeX does not use a glyph from the font for the horizontal lines in fractions and square roots, it just draws them as a rule, so there is no "frac line" than comes from the font. –  David Carlisle Apr 22 '13 at 16:06
ok, but is there a way to fix the height with which draw the rule of the over bar? This could allow me to use easily the square roots of mh3 –  Lorenzo Apr 22 '13 at 16:17
@Lorenzo as I said in the answer, you either need to build a virtual font in which the symbol is lowered or you need to not use the \radical primitive and just use \sqr\overline{a} wher e\sqr is defined by something like \DeclareMathSymbol{\sqr}{\mathord}{letters}{'317} –  David Carlisle Apr 22 '13 at 16:28

It is not exactly an answer, but I can see that you are interested in modifying the radical sign. There is a very interesting attempt to this problem: http://www.gust.org.pl/bachotex/2011/program (Marek Ryćko, A Radical Approach to the Radical Sign).

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I have solved my question using \strut and other instructions (in order to adjust the height), which fix the height of the over bar. Actually, I'm using \surd and \radicando macros; the latter is described below.

    \def\radicando#1{%
\leavevmode
\kern-.5pt\hbox{%
\vtop{%
\vbox{%
\hrule\kern .25pt
\hbox{%
\kern 1pt \strut#1\kern 0pt
}%
}%
\kern -3pt
}%
}
}

\def\radice#1{\surd\radicando{\hbox{$#1$}}}


These allow me to create the square root sign (of mh3) and a radicant environment. In addition, when I need a non-square root, I can use the ordinary \sqrt[n]{#1} instruction, as shown in the following picture

Anyway, I'm using it because I want to set some macros that allow me to use the mathematical pi font volume. I know that these glyphs represent a non-standard TeX character and I would not recommend it to anyone.

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Otherwise, I could use \def\radice#1{\surd\kern-.25pt\overline{\mathstrut#1}} instruction. –  Lorenzo Apr 23 '13 at 21:44