Vrftjkry

I understand that this request may sound stupid, but my eyes are just bleeding when I see how $frac{x^-}{2}$ is rendered:

I'm wondering if there's a moderately simple way to make it look like this?

(Please do not suggest $frac{x^-}{2^{phantom{-}}}$ or $frac{{}^{phantom{-}}x^-}{2}$.)

UPDATE

Well, OK, I've realized that frac{x}{2}^{-} may work as a temporary solution, but now my eyes are bleeding when looking at the source code.

My eyes bleed with your proposal. Anyway

documentclass{article}

usepackage{amsmath}



makeatletter

newcommand{fracto}[3]{%

  {mathpalettefrac@to{{#1}{#2}{#3}}}%

}

newcommand{frac@to}[2]{frac@@to#1#2}

newcommand{frac@@to}[4]{%

  % #1 = mathstyle

  % #2 = full numerator

  % #3 = denominator

  % #4 = reduced numerator

  begingroup

  sboxz@{$m@th#1frac{#2}{#3}$}%

  sboxtw@{$m@th#1frac{#4}{#3}$}%

  settowidthdimen@{$m@thfrac@to@demote#1#4$}%

  frac{{}makebox[dimen@][l]{$frac@to@demote#1#2$}}{#3}%

  kern-wdtw@

  kernwdz@

  endgroup

}

newcommandfrac@to@demote[1]{%

  ifx#1displaystyletextstyleelse

  ifx#1textstylescriptstyleelse

  scriptscriptstylefifi

}

makeatother



begin{document}



begin{gather*}

X + frac{x^{-}}{2} + frac{x^{-}}{100} + X \

X + fracto{x^{-}}{2}{x} + fracto{x^{-}}{100}{x} + X \

end{gather*}



end{document}

First I typeset the standard fraction, then the same but with the “reduced numerator” in two boxes, so I can use their widths. I also measure the reduced numerator.

Then I typeset the fraction with the numerator having the same width as the reduced one (aligned left). This fraction is as wide as box 2, so I back up by this amount and reinstate the width of the standard fraction, which is the width of box 0.

I'll be happy to remove this but you could do

documentclass{article}

usepackage{mathtools}

begin{document}

[frac{x^{mathrlap{-}}}{2}hphantom{scriptstyle -}x]

end{document}