r=1/%s /// \sleftarrow{\normalfont defining a rational number}
a=[1,r;1,1]  /// \sleftarrow{\normalfont rational matrix construction}
b=inv(a)  /// \sleftarrow{\normalfont matrix inversion}
b.num  /// \sleftarrow{\normalfont numerator field}
b.den /// \sleftarrow{\normalfont denominator field}