org.scijava.parse.eval.Evaluator Maven / Gradle / Ivy
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* Parsington: the SciJava mathematical expression parser.
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package org.scijava.parse.eval;
import java.util.LinkedList;
import java.util.Map;
import org.scijava.parse.ExpressionParser;
import org.scijava.parse.SyntaxTree;
import org.scijava.parse.Variable;
/**
* Interface for expression evaluators.
*
* @author Curtis Rueden
*/
public interface Evaluator {
/** Gets the parser used when evaluating expressions. */
ExpressionParser getParser();
/**
* Gets whether the evaluator is operating in strict mode.
*
* @see #setStrict(boolean)
*/
boolean isStrict();
/**
* 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 {@link IllegalArgumentException}
* with an "Unknown variable" message; in non-strict mode, such a variable
* will instead be resolved to an object of type {@link 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 {@code foo=bar} will complete
* successfully in non-strict mode, with the variable {@code foo} containing
* an object of type {@link Unresolved} and token value {@code "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
* {@link DefaultEvaluator} will fail with an "Unsupported binary operator"
* exception when given the expression {@code foo+bar}, since {@code foo} and
* {@code bar} are unresolved variables, and the {@code +} operator cannot
* handle such objects.
*
*/
void setStrict(boolean strict);
/** Evaluates the given infix expression, returning the result. */
Object evaluate(final String expression);
/** Evaluates the given postfix token queue, returning the result. */
Object evaluate(final LinkedList