From: sushil r. <ron...@gm...> - 2007-04-20 13:59:45
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Thanks Examples You have given are sufficient to understand me the concept behind precedence. Now it is easy for me to implement matcher code for all of this. On 4/20/07, Nina Jeliazkova <ni...@ac...> wrote: > Hello, > > & and ; both mean logical AND, and both translate to the same Java AND > operator. The difference is how the operands are grouped (precedence). Jiao > is > absolutely right, the standard approach for any parsers to resolve operator > precedences is to use proper data structure (a tree or if I remember right a > stack could also do). > > Examples: > 1) > [!C;R] (NOT aliphatic carbon ) AND in ring > [!C&R] NOT (aliphatic carbon AND in ring) > 2) > More > [C,N&H2] means C OR (N AND H2] > > [C,N;H2] means (C OR N) AND H2 > > > Hope this helps, > Nina > > > "sushil ronghe" <ron...@gm...> wrote: > > > I mean how should i implement the matching in matcher class > > SMARTSOperatorAtom > > > > > > > The highest precedence expression should be left last to parse > > > > > > ok this is quite useful to me but my question was, > > i want to know for matching what is the equivalent operator in java for & > > and ; > > suppose we have expression like this [C,N&H2] and [C,N;H2] > > what is the difference in between this two. > > > > for both the operators this is true [C or N and H2] > > or something else. > > > > > > > > > > > > > > > > On 4/20/07, Jiao, Dazhi <dj...@in...> wrote: > > > > > > Sushil, > > > > > > When parsing a language with binary operators, the TREE structure is the > > > key. > > > > > > To do precedence, please refer to my previous email about a > > > "LogicalOperator" class and my JJTree code. > > > > > > The BNF I created for parsing binary operators is: > > > > > > LogicalExpression ::= "[" AndOrExpression "]" > > > LowAndExpression ::= OrExpression ( ";" LowAndExpression )? > > > OrExpression ::= ExplicitHighAndExpression ( "," OrExpression ) ? > > > ExplicitHighAndExpression ::= ImplicitHighAndExpression ( "&" > > > ExplicitHighAndExpression )? > > > ImplicitHighAndExpression ::= NotExpression ( ImplicitHighAndExpression > ) > > > ? > > > > > > The highest precedence expression should be left last to parse. As you > > > can see, this basically will create a partial binary parse tree. > > > > > > Logical bonds are similar to this. > > > > > > I hope this helps. and I really suggest you to take a look at the BNF I > > > created. It's in the previous email and in the JJTree code. I made > > > a little changes to add ring identifiers. But the basic structure is the > > > same. Even if we decide on JavaCC instead of JJTree, a BNF is > > > always helpful to have a full picture of the language. > > > > > > David > > > > > > sushil ronghe wrote: > > > > > > > > As a smart parser has completed a significant part of smarts > expression. > > > > i think this is the time to incorporate aromatic atom,and support for > > > > expressions > > > > like atom with hydrogenes.Ex :c:[nH1] or [CH2] etc.. that will be > > > > done easily. > > > > > > > > But in operator precedence i am really unable to think how should one > > > > implement that. > > > > at present for both these operator "&" and ";" i have added the > > > > "*and"* operator see the file > > > > SMARTSOperatorAtom in > "org.openscience.cdk.isomorphism.matchers.smarts". > > > > > > > > please help me to understand operator precedence. > > > > > > > > -- > > > > ******************************** > > > > sushil ronghe > > > > Center of Pharmacoinformatics > > > > India > > > > ********************************* > > > > > ------------------------------------------------------------------------ > > > > > > > > > > > > ------------------------------------------------------------------------- > > > > This SF.net email is sponsored by DB2 Express > > > > Download DB2 Express C - the FREE version of DB2 express and take > > > > control of your XML. No limits. Just data. Click to get it now. > > > > http://sourceforge.net/powerbar/db2/ > > > > > ------------------------------------------------------------------------ > > > > > > > > _______________________________________________ > > > > Cdk-devel mailing list > > > > Cdk...@li... > > > > https://lists.sourceforge.net/lists/listinfo/cdk-devel > > > > > > > > > > > > > > > > > -- ******************************** sushil ronghe Center of Pharmacoinformatics India ********************************* |