weka.core.expressionlanguage.core

Interface VariableDeclarations

All Superinterfaces:

Serializable

All Known Implementing Classes:

InstancesHelper, NoVariables, SimpleVariableDeclarations, StatsHelper, VariableDeclarationsCompositor

public interface VariableDeclarations
extends Serializable

Interface to expose variables to a program.

It is deliberately kept very simple to give as little constraints as possible to implementations.

There is an implied invariant here:
hasVariable(String) == true -> getVariable(String) != null

hasVariable(String) should be pure i.e. have no side effects.
Whereas getVariable(String) may have side effects.
(This is useful for creating variables on the fly in getVariable(String))

Version:

$Revision: 1000 $

Author:

Benjamin Weber ( benweber at student dot ethz dot ch )

Method Summary

Modifier and Type	Method and Description
Node	getVariable(String name) Tries to fetch a variable
boolean	hasVariable(String name) Whether the variable is declared

Method Detail

hasVariable

boolean hasVariable(String name)

Whether the variable is declared

Parameters:

name - name of the variable being queried

Returns:

whether the variable is declared

getVariable

Node getVariable(String name)

Tries to fetch a variable

Before a variable is fetched it should be checked whether it is declared through hasVariable(String).

Parameters:

name - name of the variable to be fetched

Returns:

an AST (abstract syntax tree) node representing the variable