Added RExp#addAttribute(String, RExp) method

pmml-rexp/src/main/java/org/jpmml/rexp/RExp.java

@@ -141,6 +141,32 @@ private RExp findAttribute(String name, boolean required){
 		return null;
 	}
 
+	public void addAttribute(String name, RExp rexp){
+		addAttribute(new RPair(new RString(name), rexp, null));
+	}
+
+	public void addAttribute(RPair pair){
+		RPair attributes = getAttributes();
+
+		if(attributes == null){
+			setAttributes(pair);
+
+			return;
+		}
+
+		while(attributes != null){
+			RPair next = attributes.getNext();
+
+			if(next == null){
+				break;
+			}
+
+			attributes = next;
+		}
+
+		attributes.setNext(pair);
+	}
+
 	public RPair getAttributes(){
 		return this.attributes;
 	}

pmml-rexp/src/test/java/org/jpmml/rexp/RGenericVectorTest.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2024 Villu Ruusmann
+ *
+ * This file is part of JPMML-R
+ *
+ * JPMML-R is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * JPMML-R is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with JPMML-R.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.jpmml.rexp;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class RGenericVectorTest {
+
+	@Test
+	public void addAttributes(){
+		List<RExp> values = Arrays.asList(
+			new RIntegerVector(Collections.emptyList(), null),
+			new RDoubleVector(Collections.emptyList(), null),
+			new RStringVector(Collections.emptyList(), null)
+		);
+
+		RGenericVector genericVector = new RGenericVector(values, null);
+
+		assertFalse(genericVector.hasAttribute("class"));
+		assertFalse(genericVector.hasAttribute("names"));
+
+		genericVector.addAttribute("class", new RStringVector(Arrays.asList("data.frame"), null));
+
+		assertTrue(genericVector.hasAttribute("class"));
+		assertFalse(genericVector.hasAttribute("names"));
+
+		genericVector.addAttribute("names", new RStringVector(Arrays.asList("A", "B", "C"), null));
+
+		assertTrue(genericVector.hasAttribute("class"));
+		assertTrue(genericVector.hasAttribute("names"));
+	}
+}