com.cloudbees.groovy.cps.Block Maven / Gradle / Ivy

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package com.cloudbees.groovy.cps;

import java.io.Serializable;

/**
 * AST Node of Groovy for CPS execution.
 *
 * @author Kohsuke Kawaguchi
 */
public interface Block extends Serializable {
    /**
     * Executes this expression, then pass the result to the given continuation when it's available.
     *
     * 
     * To be more precise, this method does not evaluate the expression by itself synchronously.
     * Instead, the evaluation is done by the caller by repeatedly {@linkplain Next#step() step executing}
     * the resulting {@link Next} object.
     */
    Next eval(Env e, Continuation k);

    /**
     * A function that does nothing.
     */
    final static Block NOOP = new Noop();

    final class Noop implements Block {
        private Noop() {}

        public Next eval(Env e, Continuation k) {
            return k.receive(null);
        }

        public Object readResolve() {
            return NOOP;
        }
    }
}