sets provide the "identity" function. essentially, sets underlie the formalism to compute (or not, i.e. not-necessarily compute) whether some X == Y by value (

sets provide the "identity" function. essentially, sets underlie the formalism to compute (or not, i.e. not-necessarily compute) whether some X == Y by value (i.e. with reading the content of memory-address (pointer semantics)) and by the memory address as a value (by object in memory)