org.eclipse.viatra2.core2/src/org/eclipse/viatra2/natives/ExistsFunction.java

/*******************************************************************************
 * Copyright (c) 2004-2008 Andras Schmidt, Andras Balogh, Istvan Rath and Daniel Varro
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    Andras Schmidt, Andras Balogh, Istvan Rath - initial API and implementation
 *******************************************************************************/

package org.eclipse.viatra2.natives;

// fqn: org.eclipse.viatra2.natives.AdderFun
import org.eclipse.viatra2.core.IModelSpace;
import org.eclipse.viatra2.errors.VPMRuntimeException;
import org.eclipse.viatra2.natives.NativeFunctionParameter.ParameterType;

/**
 * Native function to provide a way for easily checking for the existence of
 * certain model elements in VTCL programs (note: the 'ref' rule throws an
 * exception if a non-existing model element is passed as the parameter, whereas
 * this native function returns "false" in that case. It returns "true" for
 * existing elements.)
 * 
 * @author Istvan Rath
 * 
 */
@VIATRANativeFunction(name = "exists", returns = ParameterType.BOOLEAN, remark = "The 'ref' rule throws an exception "
		+ "if a non-existing model element is passed as the parameter, whereas this native function "
		+ "returns \"false\" in that case.", 
		params = @NativeFunctionParameter(name = "elements", 
				description = "FQNs of model elements to be checked for existence", isVarArg = true, 
				type = { NativeFunctionParameter.ParameterType.STRING }))
public class ExistsFunction implements ASMNativeFunction {

	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.eclipse.viatra2.natives.ASMNativeFunction#evaluate(org.eclipse.viatra2
	 * .core.IModelSpace, java.lang.String[])
	 */
	public Object evaluate(IModelSpace msp, Object[] params)
			throws VPMRuntimeException {
		boolean allOK = true;
		for (Object ref : params) {
			if (ref instanceof String)
				allOK &= (msp.getModelManager().getElementByName((String) ref) != null);
			else
				throw new VPMRuntimeException("Parameter type mismatch!");
		}
		return allOK;
	}

	public String getName() {
		return "exists"; // VTCL
	}

	public String getDescription() {
		return "checks for the existence of model elements; returns \"true\" if all parameters exist, \"false\" otherwise";
	}

	public String getID() {
		return this.getClass().getCanonicalName();
	}

}