void action is used to evaluate an expression, but to throw away
the resulting value. This is useful when the expression has
side-effects that are desired, but the actual value generated by the
expression is of no interest.
expression must be an expression of an unqualified type: that is,
switch, an opaque type, or a record type. If
expression is of type
string source, it is first implicitly
converted to a
string; this drains expression.
Although expression can be any expression of an unqualified type,
the most common use of
void is when expression contains a function
process local integer i set i to system-call "<operating system command>"
which generates a warning (because the shelf I is assigned a value but
never used), the following can be written
process void system-call "<operating system command>"