org.scijava.parse.eval

Interface Evaluator

All Known Subinterfaces:

StackEvaluator, StandardEvaluator

All Known Implementing Classes:

AbstractEvaluator, AbstractStackEvaluator, AbstractStandardStackEvaluator, DefaultEvaluator

public interface Evaluator

Interface for expression evaluators.

Author:

Curtis Rueden

Method Summary

Methods

Modifier and Type	Method and Description
Object	evaluate(LinkedList<Object> queue) Evaluates the given postfix token queue, returning the result.
Object	evaluate(String expression) Evaluates the given infix expression, returning the result.
Object	evaluate(SyntaxTree syntaxTree) Evaluates the given syntax tree, returning the result.
Object	get(Variable v) Gets the value of the given variable.
ExpressionParser	getParser() Gets the parser used when evaluating expressions.
boolean	isStrict() Gets whether the evaluator is operating in strict mode.
void	set(Variable v, Object value) Sets the value of the given variable.
void	setAll(Map<? extends String,? extends Object> map) Assigns variables en masse.
void	setStrict(boolean strict) Sets whether the evaluator is operating in strict mode.
Object	value(Object token) Gets the value of the given token.

Method Detail

getParser

ExpressionParser getParser()

Gets the parser used when evaluating expressions.

isStrict

boolean isStrict()

Gets whether the evaluator is operating in strict mode.

See Also:

setStrict(boolean)

setStrict

void setStrict(boolean strict)

Sets whether the evaluator is operating in strict mode. Evaluators operate in strict mode by default.

When evaluating strictly, usage of an unassigned variable token in a place where its value is needed will generate an IllegalArgumentException with an "Unknown variable" message; in non-strict mode, such a variable will instead be resolved to an object of type Unresolved with the same name as the original variable.

In cases such as assignment, this may be sufficient to complete the evaluation; for example, the expression foo=bar will complete successfully in non-strict mode, with the variable foo containing an object of type Unresolved and token value "bar". But in cases where the unresolved value is needed as an input for additional operations, the evaluation may still ultimately fail of the operation in question is not defined for unresolved values. For example, the DefaultEvaluator will fail with an "Unsupported binary operator" exception when given the expression foo+bar, since foo and bar are unresolved variables, and the + operator cannot handle such objects.

evaluate

Object evaluate(String expression)

Evaluates the given infix expression, returning the result.

evaluate

Object evaluate(LinkedList<Object> queue)

Evaluates the given postfix token queue, returning the result.

evaluate

Object evaluate(SyntaxTree syntaxTree)

Evaluates the given syntax tree, returning the result.

value

Object value(Object token)

Gets the value of the given token. For variables, returns the value of the variable, throwing an exception if the variable is not set. For literals, returns the token itself.

get

Object get(Variable v)

Gets the value of the given variable.

set

void set(Variable v,
       Object value)

Sets the value of the given variable.

setAll

void setAll(Map<? extends String,? extends Object> map)

Assigns variables en masse.