Interpreters for general purpose programming languages are serious programs. In particular, the interpreters we wrote for ps11 are serious programs. As you have seen from the sieve and vectors example programs, ps11 is powerful enough to define structured data types. With a few extensions to its concrete syntax, a type checker, and a way to call library routines written in another language, ps11 would be more than competitive with languages such as Python. All of that could be added without making any changes to the ps11 interpreters we've already written.

We can therefore use those interpreters as examples of serious Java programs that would benefit from proper tail recursion.

Let's use the sieve.ps11 program as a benchmark to compare the performance of one of those interpreters, written in Java, to a ps11 compiler (also written in Java) that generates Scheme code, which can then be executed by any implementation of the current Scheme standard.