Relevant: http://www.daimi.au.dk/~madst/tool/papers/expression.txt http://www.daimi.au.dk/~madst/tool/papers/expression.txt The salient paragraph: "Whether a l

Relevant: http://www.daimi.au.dk/~madst/tool/papers/expression.txt http://www.daimi.au.dk/~madst/tool/papers/expression.txt The salient paragraph: "Whether a language can solve the Expression Problem is a salient indicator of its capacity for expression. One can think of cases as rows and functions as columns in a table. In a functional language, the rows are fixed (cases in a datatype declaration) but it is easy to add new columns (functions). In an object-oriented language, the columns are fixed (methods in a class declaration) but it is easy to add new rows (subclasses). We want to make it easy to add either rows or columns."