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Re: [ddlm-group] Characterset of non-delimited strings insidecompound data items
- To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
- Subject: Re: [ddlm-group] Characterset of non-delimited strings insidecompound data items
- From: "Herbert J. Bernstein" <yaya@bernstein-plus-sons.com>
- Date: Mon, 8 Nov 2010 21:23:01 -0500 (EST)
- In-Reply-To: <AANLkTimVXn5ZEEBZx37YtgjP3g8AdZGZEise7fF=C+Ee@mail.gmail.com>
- References: <AANLkTimVXn5ZEEBZx37YtgjP3g8AdZGZEise7fF=C+Ee@mail.gmail.com>
While I have no particular objection to excluding the close brackets from non-delimited strings, personally I think making easy use of flex a criterion for the design of CIF2 is not a good idea. -- Herbert ===================================================== Herbert J. Bernstein, Professor of Computer Science Dowling College, Kramer Science Center, KSC 121 Idle Hour Blvd, Oakdale, NY, 11769 +1-631-244-3035 yaya@dowling.edu ===================================================== On Tue, 9 Nov 2010, James Hester wrote: > 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 > _______________________________________________ ddlm-group mailing list ddlm-group@iucr.org http://scripts.iucr.org/mailman/listinfo/ddlm-group
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