anchor.diff:  
   There are several ways of using function queries in a Solr query:
   
  -* Via an explicit QParser that expects function arguments, such <<other-parsers.adoc#function-query-parser,`func`>> or <<other-parsers.adoc#function-range-query-parser,`frange`>>. For example:
  +* Via an explicit query parser that expects function arguments, such <<other-parsers.adoc#function-query-parser,`func`>> or <<other-parsers.adoc#function-range-query-parser,`frange`>>. For example:
   +
   [source,text]
   ----
  
positive.code: <float name="score">0.343</float>
  ...
  ----
  * Use in a parameter that is explicitly for specifying functions, such as the EDisMax query parser's <<the-extended-dismax-query-parser.adoc#the-extended-dismax-query-parser,`boost`>> param, or DisMax query parser's <<the-dismax-query-parser.adoc#bf-boost-functions-parameter,`bf` (boost function) parameter>>. (Note that the `bf` parameter actually takes a list of function queries separated by white space and each with an optional boost. Make sure you eliminate any internal white space in single function queries when using `bf`). For example:
  +
  [source,text]
  ----
  q=dismax&bf="ord(popularity)^0.5 recip(rord(price),1,1000,1000)^0.3"
  ----
  * Introduce a function query inline in the lucene QParser with the `\_val_` keyword. For example:
  +
  [source,text]
  ----
  
negative.code: 
  To give you a better understanding of how function queries can be used in Solr, suppose an index stores the dimensions in meters x,y,z of some hypothetical boxes with arbitrary names stored in field `boxname`. Suppose we want to search for box matching name `findbox` but ranked according to volumes of boxes. The query parameters would be:
  
  [source,text]
  q=boxname:findbox _val_:"product(x,y,z)"
  
  This query will rank the results based on volumes. In order to get the computed volume, you will need to request the `score`, which will contain the resultant volume:
  
  [source,text]
  &fl=*, score
  
  Suppose that you also have a field storing the weight of the box as `weight`. To sort by the density of the box and return the value of the density in score, you would submit the following query:
  
  