2011-07-23 ago defer evaluation of Scan.message, for improved performance in the frequent situation where failure is handled later (e.g. via ||);
2011-07-12 ago more precise Symbol_Pos.quote_string;
2011-07-08 ago discontinued special treatment of hard tabulators;
2011-04-30 ago more uniform variations of scan_string;
2010-12-29 ago more scalable Symbol_Pos.explode;
2010-11-13 ago eliminated slightly odd pervasive Symbol_Pos.symbol;
2010-05-17 ago tuned signature;
2009-09-30 ago eliminated redundant bindings;
2009-03-19 ago moved basic change_prompt, scan_string, scan_alt_string, scan_quoted to symbol_pos.ML;
2009-03-18 ago de-camelized Symbol_Pos;
2009-01-21 ago removed Ids;
2008-08-24 ago untabify: silently turn tab into space if column information is unavailable;
2008-08-14 ago made SML/NJ happy;
2008-08-13 ago added untabify_content;
2008-08-09 ago added content;
2008-08-07 ago renamed SymbolPos.scan_position to SymbolPos.scan_pos;
2008-08-07 ago Symbols with explicit position information.