This is an example implementation of a simple pure ML-like functional language with a non-standard control flow mechanism, which we can call functional jump for now.
It is a simple generalized control flow mechanism for implementing both iteration and branching. Roughly speaking, it tries to unify the following concepts:
- pattern matching
- ad-hoc exception introduction and handling
- goto (yay! the considered-harmful one!)
- related to continuations
A function computing the sum of the first n integers:
let sum = fun n ->
>> (n, 0) where
| (0, acc) -> acc
| (k, acc) -> >> (k-1, acc+k)
end
Potentially, this mechanism can be useful for simplifying recursive function definitions that describe iterations, but involve complicated logic or order of execution that is painful to express in a clear way with normal recursion.
It provides seamless integration of finite-automaton-like control flow into a functional language. Kinda wondering if there is any relation to co-induction or any other fancy topics.
It seems that the correctness of labels and jumps can be statically type-checked, but I haven't proved it yet.
You have to install ocaml compiler and menhir parser generator.
It is recommended to use OCaml package manager opam to install menhir.
make
./jump < test/sum.jump
In addition, the file "jump.vim" provides some basic syntax highlighting for Vim text editor. (Please follow/search for the official Vim instructions for installing such syntax files.)
- Practically no error reporting.
- No documentation about this control flow mechanism.
- Edsger Dijkstra (March 1968). "Go To Statement Considered Harmful". Communications of the ACM 11 (3): 147–148.
The software is distributed under the conditions of the BSD 3-clause license.