Conceptually, dbc checks are on states, and hence occur between refs and defs. eg https://se.inf.ethz.ch/~meyer/publications/old/dbc_chapter.pdf https://se.inf

Conceptually, dbc checks are on states, and hence occur between refs and defs. eg https://se.inf.ethz.ch/~meyer/publications/old/dbc_chapter.pdf https://se.inf.ethz.ch/~meyer/publications/old/dbc_chapter.p... > If both the client and the routine check for the same conditions, the resulting redundancy, when accumulated over a large system, will yield the complexity and unwieldiness that are so characteristic of today's software. ... better check twice than not at all, reason the designers.