Ko te Weierstrass, Cantor, me Heine e tu ana i a rātau ariā i runga i ngā rangatū mutunga kore, i kitea e te Dedekind tōna ariā mō tētahi tapahi (Schnitt) i roto i te pūnaha o ngā tau tūturu, e wehe ana i ngā tau hautanga katoa ki ngā rōpū e rua whai āhuatanga.