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
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public interface Expression
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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

Methods
Modifier and Type	Method and Description
`void`	`addExpressionListener(ExpressionListener lstnr)` 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 lstnr)` Remove a listener to this Expression.
`void`	`visit(ExpressionVisitor v)` Passes the visitor through this expression and any sub expressions

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

Interface Expression

Method Summary

Method Detail

getType

visit

get

getInt

getLong

getFloat

getDouble

getBoolean

addExpressionListener

removeExpressionListener