Mixed number with slanted fraction

Question

I wanted to use some mixed numbers with slanted fraction in my text, so I used \sfrac or \nicefrac, as recommended by S. Kottwitz.

\documentclass{article}
\usepackage{amsmath}
\usepackage{xfrac}
\usepackage{nicefrac}
\begin{document}
\noindent
A not slanted mixed number with \verb|\frac| : (2\frac{1}{2}), (4\frac{3}{7})\
A mixed number with \verb|\sfrac|: (2\sfrac{1}{2}), (4\sfrac{3}{7})\
A mixed number with \verb|\nicefrac|: (2\nicefrac{1}{2}), (4\nicefrac{3}{7})
\end{document}

But the visual results were not appealing to me. See on the picture how the numerators 1 of 1/2 and 3 of 3/7 look more like the exponents of 2 and 4 respectively. Admittedly, the \nicefrac outputs a nicer output than \sfrac, however not yet satisfying.

How can I improve the spacing of the mixed number with the slanted fraction so that the main number and the fraction's numerator look better?

Answer 1

If there is font feature +frac in used font then it is much better to use it instead of to crate a macro which build the fraction from slash and other components. The font designer implements better look of the fraction: suggests better size for numbers and creates (typically) another slant for slash.

Compare following example in Libertine font:

This example was created by following code in OpTeX:

\fontfam[libertine]
\def\sfrac#1/#2 {\raise.75ex\hbox{$\scriptstyle #1\mkern-5mu$}/%
   \lower.35ex\hbox{$\scriptstyle\mkern-4mu#2$}}
fontfeature: {\setff{+frac}\rm 2,1/2}
macro: $2,\sfrac 1/2 $
\bye

Answer 2

To control the spacing in a mixed number, I add the math horizontal spacing \mspace{<number of mus>mu} to the mixed number with \sfrac (1mu = 1/18em).

My preferred look is adding 1mu extra space between number and slanted fraction, and -3mu extra space between numerator and the slash of the fraction. Thus, I define following command \mixednumber for "nicer" mixed numbers:

%needs packages 'xfrac' for \sfrac, 'amsmath' for \mspace
\newcommand*{\mixednumber}[3]{\ensuremath{#1\mspace{1mu}\sfrac{#2\mspace{-3mu}}{#3}}}

You can adapt the distances by accordingly changing 1mu or -3mu with the preferred spaces. You can even modify the spacing at the denominator by adding the corresponding \mspace before the #3 argument, though, for me, the denominator looks great. ;)

See the minimal example:

\documentclass{article}
\usepackage{amsmath}
\usepackage{xfrac}
\usepackage{nicefrac}
%needs packages 'xfrac' for \sfrac, 'amsmath' for \mspace
\newcommand*{\mixednumber}[3]{\ensuremath{#1\mspace{1mu}\sfrac{#2\mspace{-3mu}}{#3}}}
\begin{document}
\noindent
A not slanted mixed number with \verb|\frac| : (2\frac{1}{2}), (4\frac{3}{7})\
A mixed number with \verb|\sfrac|: (2\sfrac{1}{2}), (4\sfrac{3}{7})\
A mixed number with \verb|\nicefrac|: (2\nicefrac{1}{2}), (4\nicefrac{3}{7})\
A mixed number with \verb|\mixednumber|: \mixednumber{2}{1}{2}, \mixednumber{4}{3}{7}\
\end{document}