notation "hvbox(a break ∈ b)" non associative with precedence 45
for @{ 'mem $a $b }.
+notation "hvbox(a break ∉ b)" non associative with precedence 45
+for @{ 'notmem $a $b }.
+
notation "hvbox(a break ≬ b)" non associative with precedence 45
for @{ 'overlaps $a $b }. (* \between *)