WriteLn

src/interpreter/Preprocessor.kt

@@ -148,6 +148,7 @@ open class Preprocessor {
                     // IO
                     Functor.of("write/1") -> Write(args[0])
                     Functor.of("nl/0") -> Nl
+                    Functor.of("writeln/1") -> WriteLn(args[0])
                     Functor.of("read/1") -> Read(args[0])
 
                     // Lists

src/prolog/builtins/ioOperators.kt

@@ -17,6 +17,8 @@ import prolog.logic.unifyLazy
  * Write [Term] to the current output, using brackets and operators where appropriate.
  */
 class Write(private val term: Term) : Operator(Atom("write"), null, term), Satisfiable {
+    constructor(message: String) : this(Atom(message))
+
     override fun satisfy(subs: Substitutions): Answers {
         val t = applySubstitution(term, subs)
 
@@ -45,6 +47,11 @@ object Nl : Atom("nl"), Satisfiable {
     override fun applySubstitution(subs: Substitutions): Nl = this
 }
 
+class WriteLn(private val term: Term) : Conjunction(Write(term), Nl) {
+    constructor(message: String) : this(Atom(message))
+    override fun applySubstitution(subs: Substitutions): WriteLn = WriteLn(applySubstitution(term, subs))
+}
+
 /**
  * Read the next Prolog term from the current input stream and unify it with [Term].
  *