Expression

All Known Subinterfaces:

Function, Predicate

All Known Implementing Classes:

AbstractExpression, AbstractPredicate, AndPredicate, ArithmeticExpression, BinaryExpression, BooleanLiteral, ColumnExpression, ComparisonPredicate, CompositePredicate, FunctionExpression, GroupExpression, GroupSizeFunction, HoverPredicate, IfExpression, InGroupPredicate, Literal, NotPredicate, NumericLiteral, ObjectLiteral, OrPredicate, QueryExpression, RangePredicate, SearchPredicate, StartVisiblePredicate, ValidatedPredicate, ValidEdgePredicate, VisiblePredicate, XorPredicate
```
public interface Expression
```
An Expression is an arbitrary function that takes a single Tuple as an argument. Expressions support both Object-valued and primitive-valued (int, long, float, double, boolean) evaluation methods. The appropriate method to call depends on the particular Expression implementation. A getType(Schema) method provides mechanism for determining the return type of a given Expression instance. A Predicate is an Expression which is guaranteed to support the getBoolean(Tuple) method, is often used to filter tuples.

Expressions also support a listener interface, allowing clients to monitor changes to expressions, namely rearrangements or modification of contained sub-expressions. The Expression interface also supports visitors, which can be used to visit every sub-expression in an expression tree.

Using the various Expression implementations in the Expression package, clients can programatically construct a tree of expressions for use as complex query predicates or as functions for computing a derived data column (see Table.addColumn(String, Expression). Often it is more convenient to write expressions in the prefuse expression language, a SQL-like data manipulation language, and compile the Expression tree using the ExpressionParser. The documentation for the ExpressionParser class includes a full reference for the textual expression language.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`void`	`addExpressionListener(ExpressionListener listener)` Add a listener to this Expression.
`java.lang.Object`	`get(Tuple t)` Evaluate the Expression on the given input Tuple.
`boolean`	`getBoolean(Tuple t)` Evaluate the Expression on the given input Tuple.
`double`	`getDouble(Tuple t)` Evaluate the Expression on the given input Tuple.
`float`	`getFloat(Tuple t)` Evaluate the Expression on the given input Tuple.
`int`	`getInt(Tuple t)` Evaluate the Expression on the given input Tuple.
`long`	`getLong(Tuple t)` Evaluate the Expression on the given input Tuple.
`java.lang.Class`	`getType(Schema s)` Returns the type that this expression evaluates to when tuples with the given Schema are provided as input.
`void`	`removeExpressionListener(ExpressionListener listener)` Remove a listener to this Expression.
`void`	`visit(ExpressionVisitor v)` Passes the visitor through this expression and any sub expressions

- Method Detail
  - getType
```
java.lang.Class getType(Schema s)
```
    Returns the type that this expression evaluates to when tuples with the given Schema are provided as input.
  - visit
```
void visit(ExpressionVisitor v)
```
    Passes the visitor through this expression and any sub expressions
    
    Parameters:
    
    v - the ExpressionVisitor
  - get
```
java.lang.Object get(Tuple t)
```
    Evaluate the Expression on the given input Tuple.
    
    Parameters:
    
    t - the input Tuple
    
    Returns:
    
    the Expression return value, as an Object
  - getInt
```
int getInt(Tuple t)
```
    Evaluate the Expression on the given input Tuple.
    
    Parameters:
    
    t - the input Tuple
    
    Returns:
    
    the Expression return value, as an int
  - getLong
```
long getLong(Tuple t)
```
    Evaluate the Expression on the given input Tuple.
    
    Parameters:
    
    t - the input Tuple
    
    Returns:
    
    the Expression return value, as a long
  - getFloat
```
float getFloat(Tuple t)
```
    Evaluate the Expression on the given input Tuple.
    
    Parameters:
    
    t - the input Tuple
    
    Returns:
    
    the Expression return value, as a float
  - getDouble
```
double getDouble(Tuple t)
```
    Evaluate the Expression on the given input Tuple.
    
    Parameters:
    
    t - the input Tuple
    
    Returns:
    
    the Expression return value, as a double
  - getBoolean
```
boolean getBoolean(Tuple t)
```
    Evaluate the Expression on the given input Tuple.
    
    Parameters:
    
    t - the input Tuple
    
    Returns:
    
    the Expression return value, as a boolean
  - addExpressionListener
```
void addExpressionListener(ExpressionListener listener)
```
    Add a listener to this Expression.
    
    Parameters:
    
    listener - the expression listener to add
  - removeExpressionListener
```
void removeExpressionListener(ExpressionListener listener)
```
    Remove a listener to this Expression.
    
    Parameters:
    
    listener - the expression listener to remove

Interface Expression

Method Summary

Method Detail

getType

visit

get

getInt

getLong

getFloat

getDouble

getBoolean

addExpressionListener

removeExpressionListener