Unlike most other programming languages, which are not stropped, in
Algol 68 it is possible to have tags with the same name as reserved
words, by appending an underscore character to the tag. For example, a
tag if can be written as if_. It is important to note
that the trailing underscore is not part of the tag: it is just a
stropping artifact. This is always better than contriving artificious
synonyms that are often confusing or too long. A copying routine has
arguments "from" and "to"? Call them from_ and to_. A
struct mode has fields "in" and "out"? Call them in_ and
out_.
Please use fully upper-case bold words for operator indicants. This
makes it easier for text editors to highlight them in a different
style than mode indicants, and look more symmetrical in case of dyadic
operators. For example, use ABS and not Abs.