The conic hull of a set $X$ is $\cone{X}$; its affine hull is
$\aff{X}$, and its convex hull is $\conv{X}$. If $K$ is a cone,
then its lineality space is $\linspace{K}$, its lineality is
The conic hull of a set $X$ is $\cone{X}$; its affine hull is
$\aff{X}$, and its convex hull is $\conv{X}$. If $K$ is a cone,
then its lineality space is $\linspace{K}$, its lineality is
- $\lin{K}$, and its extreme directions are $\Ext{K}$.
+ $\lin{K}$, and its extreme directions are $\Ext{K}$. The fact that
+ $F$ is a face of $K$ is denoted by $F \faceof K$; if $F$ is a
+ proper face, then we write $F \properfaceof K$.