Fix double printing

src/Main.kt

@@ -1,11 +1,8 @@
-import com.sun.org.apache.bcel.internal.util.Args
 import com.xenomachina.argparser.ArgParser
 import com.xenomachina.argparser.mainBody
 import interpreter.FileLoader
 import io.GhentPrologArgParser
 import io.Logger
-import prolog.Program
-import prolog.ast.logic.Clause
 import repl.Repl
 
 fun main(args: Array<String>) = mainBody {

src/interpreter/Preprocessor.kt

@@ -2,6 +2,7 @@ package interpreter
 
 import io.Logger
 import prolog.ast.arithmetic.Expression
+import prolog.ast.arithmetic.Integer
 import prolog.ast.logic.Clause
 import prolog.ast.logic.Fact
 import prolog.ast.logic.LogicOperand
@@ -56,6 +57,8 @@ open class Preprocessor {
             Structure(Atom("fail"), emptyList()) -> Fail
             Atom("!") -> Cut()
             Structure(Atom("!"), emptyList()) -> Cut()
+            Atom("inf") -> Integer(Int.MAX_VALUE)
+            Atom("nl") -> Nl
             is Structure -> {
                 // Preprocess the arguments first to recognize builtins
                 val args = term.arguments.map { preprocess(it) }
@@ -115,6 +118,10 @@ open class Preprocessor {
                         Between(args[0] as Expression, args[1] as Expression, args[2] as Expression)
                     }
 
+                    // Other
+                    term.functor == "write/1" -> Write(args[0])
+                    term.functor == "read/1" -> Read(args[0])
+
                     else -> term
                 }
             }

src/repl/Repl.kt

@@ -24,19 +24,21 @@ class Repl {
     }
 
     fun query(): Answers {
-        val queryString = io.prompt("?-", { "" })
+        val queryString = io.prompt("?-", { "|  " })
         val simpleQuery = parser.parse(queryString)
         val query = preprocessor.preprocess(simpleQuery)
+        Logger.debug("Satisfying query: $query")
         return query.satisfy(emptyMap())
     }
 
     fun printAnswers(answers: Answers) {
         val knownCommands = setOf(";", "a", ".", "h")
 
-        if (answers.none()) {
+        val iterator = answers.iterator()
+
+        if (!iterator.hasNext()) {
             io.say("false.")
         } else {
-            val iterator = answers.iterator()
             var previous = iterator.next()
             io.say(prettyPrint(previous))