Enquiry clauses (GNU Algol 68 Coding Guidelines)

### 6.2 Enquiry clauses ¶

Enquiry clauses are not just “boolean expressions” with a fancy name. They can be thought as a sort of specialized serial clauses, and as such they can contain any number of declarations and units while being required to always yield a value of mode `bool`.

Avoid polluting the lexical environment with declarations that are intended to be used exclusively within conditional and loop clauses: use a declaration in the enquiry-clause of the clause instead. This also makes it easier to later refactor code.

Examples:

    { The range of `c' is the entire loop clause. }
    while char c = getchar;
          c /= char_eof
    do
       ... use c ...
    od