Package org.openrefine.grel.ast

Interface GrelExpr

All Superinterfaces:

Serializable

All Known Implementing Classes:

ArrayExpr, ControlCallExpr, FieldAccessorExpr, FunctionCallExpr, LiteralExpr, OperatorCallExpr, PureArgumentsExpr, VariableExpr

public interface GrelExpr
extends Serializable

A GREL expression, which can be evaluated in a given context.

This is introduced to serve as base class for all GREL expressions, instead of Evaluable which is the base class for all evaluables in OpenRefine.

Author:

Antonin Delpeuch

Method Summary

Modifier and Type	Method	Description
Object	evaluate(Properties bindings)	Returns the value of the expression in a given context.
Set<String>	getColumnDependencies(String baseColumn)	Returns the names of the columns this expression depends on.
boolean	isLocal()
GrelExpr	renameColumnDependencies(Map<String,String> substitutions)	Translates this expression by simultaneously substituting column names as the supplied map specifies.
String	toString()	For GREL expressions, toString should return the source code of the expression, or a source code for an equivalent expression.

Method Detail

evaluate

Object evaluate(Properties bindings)

Returns the value of the expression in a given context.

Parameters:

bindings - the evaluation context, mapping variable names to their values

Returns:

the result of the evaluation of the expression

toString

String toString()

For GREL expressions, toString should return the source code of the expression, or a source code for an equivalent expression. (without the "grel:" prefix).

Overrides:

toString in class Object

isLocal

boolean isLocal()

Returns:

true when the expression can be evaluated purely based on the local context (see Evaluable).

getColumnDependencies

Set<String> getColumnDependencies(String baseColumn)

Returns the names of the columns this expression depends on.

Parameters:

baseColumn - the name of the column this expression is based on (null if none)

Returns:

null if the columns could not be isolated: in this case, the expression might depend on all columns in the project.

renameColumnDependencies

GrelExpr renameColumnDependencies(Map<String,String> substitutions)

Translates this expression by simultaneously substituting column names as the supplied map specifies.

This is only possible if the extraction of column dependencies with getColumnDependencies(String) succeeds (return a non-null value).

Parameters:

substitutions - a map specifying new names for some columns. If a column name is not present in the map, it is assumed that the column is not renamed.

Returns:

a new expression with updated column names.