The function $f$ applied to $x$ is $f\of{x}$, and the restriction
of $f$ to a subset $X$ of its domain is $\restrict{f}{X}$. We can
group terms like $a + \qty{b - c}$ or $a + \qty{b - \sqty{c -
The function $f$ applied to $x$ is $f\of{x}$, and the restriction
of $f$ to a subset $X$ of its domain is $\restrict{f}{X}$. We can
group terms like $a + \qty{b - c}$ or $a + \qty{b - \sqty{c -