read-special in readable-snip<%>
(-> an arbitrary valuesenda-readable-snipread-specialsourcelinecolumnposition)
source: value
line: exact non-negative integer or#f
column: exact non-negative integer or#f
position: exact non-negative integer or#fThe arguments are the same as the arguments to a procedure returned by a custom input port's
read-proc; see Custom Ports, section 11.1.7 in PLT MzScheme: Language Manual for details. The result is also the same as the result from aread-proc-produced procedure.