SMARTS count matches function

This function computes the average molecular weight of an input SMILES structure. It uses the table of atomic weights and SMARTS shown in Table A.2. It relies on the count matches function described in Chapter 7. 

The matches (A,B) function returns true when SMARTS B matches SMILES A. It is sometimes useful to know how many times B matches A. For this, a new function is defined count matches (A, B). It returns an integer, possibly 0. For example, count matches ( CC (0) C, C ) returns 3. The SQF clause where count matches(cansmi, [F,Cl,Br,I] ) > 2 will find all structures having more than 2 halogen atoms. In later chapters, examples will show how this function can be used to compute molecular properties and screen structures that conform to Lipinski s Rule of 5.11... 

The following function is analogous to the fragment key function above. It uses a relational table to define fragments, a function to match SMILES and SMARTS (in this case count matches), and an aggregate SQL function to tally the results over all matched fragments. 

Create Or Replace Function count matches(text, text) Returns Integer As EOPERL use Chemistry File SMILES use Chemistry File SMARTS use Chemistry Ring 1aromatize mol1 ... 

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