Abstract

For pragmatic reasons it is useful to exclude the identity relation from the `implementable subset' of Ruby. However there are many expressions in the relational calculus whose natural meaning is just this identity relation. This note gives an identity-free account of some of these expressions, and shows that there is no satisfactory identity-free account of some others. This is an exercise in writing about Ruby without drawing any pictures, in part because it is about those expressions which would correspond to blank pictures. What there is when there is nothing there In Ruby one uses relations to represent circuit components, and the composition R ; S of relations corresponds to some connection of two components in which the parts of the R represented by its range are connected to the parts of the S represented by its domain. With this interpretation, the repeated composition R n naturally represents a `pipeline' of n components, each an R, connected in a linear array. At lea...

Citations