Guile's debugger can point back to the file and location where the
expression originated.
-The way that source properties are stored means that Guile can only
-associate source properties with parenthesized expressions, and not, for
-example, with individual symbols, numbers or strings. The difference
-can be seen by typing @code{(xxx)} and @code{xxx} at the Guile prompt
-(where the variable @code{xxx} has not been defined):
+The way that source properties are stored means that Guile cannot
+associate source properties with individual numbers, symbols,
+characters, booleans, or keywords. This can be seen by typing
+@code{(xxx)} and @code{xxx} at the Guile prompt (where the variable
+@code{xxx} has not been defined):
@example
scheme@@(guile-user)> (xxx)
properties.
@end deffn
-If the @code{positions} reader option is enabled, each parenthesized
-expression will have values set for the @code{filename}, @code{line} and
+If the @code{positions} reader option is enabled, supported expressions
+will have values set for the @code{filename}, @code{line} and
@code{column} properties.
Source properties are also associated with syntax objects. Procedural