added org.grammaticalframework.pgf.Expr.unStr

src/runtime/java/jpgf.c

@@ -1412,6 +1412,19 @@ Java_org_grammaticalframework_pgf_Expr_unMeta(JNIEnv* env, jobject self)
 	return -1;
 }
 
+JNIEXPORT jstring JNICALL
+Java_org_grammaticalframework_pgf_Expr_unStr(JNIEnv* env, jobject self)
+{
+	PgfExpr expr = gu_variant_from_ptr(get_ref(env, self));
+
+	PgfLiteralStr* pstr = pgf_expr_unlit(expr, PGF_LITERAL_STR);
+	if (pstr != NULL) {
+		return gu2j_string(env, pstr->val);
+	}
+
+	return NULL;
+}
+
 JNIEXPORT jboolean JNICALL
 Java_org_grammaticalframework_pgf_Expr_equals(JNIEnv* env, jobject self, jobject other)
 {

src/runtime/java/org/grammaticalframework/pgf/Expr.java

@@ -93,6 +93,11 @@ public class Expr implements Serializable {
 		 * a meta variable, then it will return the variable's id.
 		 * If this is not a meta variable then the result is -1. */
 		public native int unMeta();
+		
+		/** If the method is called on an expression which is 
+		 * a string literal, then it will return the string value.
+		 * If this is not a string literal then the result is null. */
+		public native String unStr();
 
 		/** Returns the expression as a string in the GF syntax */
 		public String toString() {