Function vstd::arithmetic::div_mod::lemma_div_basics

x != 0 as int ==> 0 as int / x == 0,

x / 1 == x,

x != 0 ==> x / x == 1,

Proof establishing basic properties of division using x: 0 divided by x is 0; x divided by 1 is itself; and x divided by itself is 1.