When in top level SWI-Prolog reads the user's queries using
read_history/6
rather than read/1.
This predicate first reads the current input stream up to a full stop.
While doing so it maps all contiguous blank space onto a single space
and deletes
/* ... */ and % ...<cr>
comments. Parts between double quotes (") or single quotes
(') are left unaltered. Note that a Prolog full stop
consists of a `non-symbol' character, followed by a period (.#$&*+-./:<=>?@^`~.
A single quote immediately preceded by a digit (0-9) is considered part
of the <digit>'<digit>... (e.g. 2'101;
binary number 101) sequence.
After this initial parsing the result is first checked for the
special
^<old>^<new>.
construction. If this fails the string is checked for all occurrences of
the !!?
From the above it follows that it is hard or impossible to correct quotation with single or double quotes, comment delimiters and spacing.