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