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[ddlm-group] Characterset of non-delimited strings inside compounddata items
- To: ddlm-group <ddlm-group@iucr.org>
- Subject: [ddlm-group] Characterset of non-delimited strings inside compounddata items
- From: James Hester <jamesrhester@gmail.com>
- Date: Tue, 9 Nov 2010 11:21:59 +1100
Dear DDLm group, John Bollinger has alerted me to a glitch in the current DDLm specification, to wit: (i) close bracket characters are allowed as non-final characters in a non-delimited string, and (ii) there is no requirement for whitespace between a datavalue and the close bracket symbol that denotes the end of a table or list value. This means that, in order to decide whether a close bracket character terminates a list or is just another character in the non-delimited string, the parser must look ahead, potentially many levels of nesting. For example: _t [outer [inner1 inner2]] The parser does not know that the first close bracket closes the inner list until it has read past the second close bracket. Or even more confusingly: _t [ depth_1 [ depth_2 [ depth_3 x=a1[a2[a3[a4[i]]]];]]] While this behaviour is not intractable, it is also not possible to use simple lexing tools (e.g. flex) to handle such syntax. I would therefore like to propose the following change to the current draft specification: "The characters ']' and '}' may not appear anywhere in a non-delimited datavalue" James. -- T +61 (02) 9717 9907 F +61 (02) 9717 3145 M +61 (04) 0249 4148 _______________________________________________ ddlm-group mailing list ddlm-group@iucr.org http://scripts.iucr.org/mailman/listinfo/ddlm-group
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