# Package org.apache.lucene.expressions

Expressions.

`Expression` - result of compiling an expression, which can evaluate it for a given document. Each expression can have external variables are resolved by `Bindings`.

`Bindings` - abstraction for binding external variables to a way to get a value for those variables for a particular document (DoubleValuesSource).

`SimpleBindings` - default implementation of bindings which provide easy ways to bind sort fields and other expressions to external variables

- Class Summary
  Class | Description
  --- | ---
  Bindings | Binds variable names in expressions to actual data.
  Expression | Base class that computes the value of an expression for a document.
  SimpleBindings | Simple class that binds expression variable names to `DoubleValuesSource`s or other `Expression`s.