The chapter 10 of the Algol 68 Revised Report describes the standard environment in which programs run. This chapter includes many code snippets with declarations and other entities that describe the interface provided by the standard preludes. However, code for the preludes is not given in full, suitable to be compiled form: many details are abstracted. Furthermore, the code that is actually provided in more detail is intended to serve as reference algorithms and is not necessarily the most efficient or even convenient way to encode the expressed logic.
In addition to regular comments, the code snippets in this part of the
Report use pseudo-comments, which are delimited by a pair of
bold tags c, and represent either a declarer or a
closed-clause, as suggested by the contents of the pseudo-comment.
An example of the usage of pseudo-comments from the report:
op round = (real a) int:
c An integral value, if one exists, which is
widenable to a real value differing by not more
than one-half from the value of 'a'
c;
Many other texts, articles and books in the Algol 68 sphere make use of pseudo-comments.
It may be even possible to add support to compilers so they recognize them and compile them into some appropriate run-time diagnostic, which could be helpful in top-level programming.