RootScope and support for Built in function has been added

src/main/java/serene/simple/BaseScope.java

@@ -0,0 +1,34 @@
+package serene.simple;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public abstract class BaseScope {
+  private final Map<String, Object> symbolsMapping = new HashMap<String, Object>();
+  private final BaseScope parent;
+
+  public BaseScope() {
+    this(null);
+  }
+
+  public BaseScope(BaseScope parent) {
+    this.parent = parent;
+  }
+
+  public Object lookupSymbol(String symbolName) {
+    if (this.symbolsMapping.containsKey(symbolName)) {
+      return this.symbolsMapping.get(symbolName);
+    }
+    else if (this.parent != null) {
+      return this.parent.lookupSymbol(symbolName);
+    }
+    else {
+      throw new RuntimeException(String.format("Variable '%s' is not defined in this scope.",
+                                               symbolName));
+    }
+  }
+
+  public void insertSymbol(String symbolName, Object symbolValue) {
+    this.symbolsMapping.put(symbolName, symbolValue);
+  }
+}

src/main/java/serene/simple/DefSpecialForm.java

@@ -6,7 +6,7 @@ public class DefSpecialForm extends SpecialForm {
   }
 
   @Override
-    public Object eval(Scope scope) {
+  public Object eval(BaseScope scope) {
     SymbolNode sym = (SymbolNode) this.node.rest().first();
     scope.insertSymbol(sym.name,
                        this.node.rest().rest().first().eval(scope));

src/main/java/serene/simple/FalseNode.java

@@ -4,7 +4,7 @@ public class FalseNode extends Node {
     public boolean isTruthy = false;
 
     @Override
-    public Object eval(Scope scope) {
+    public Object eval(BaseScope scope) {
         return Boolean.FALSE;
     }
 

src/main/java/serene/simple/FnSpecialForm.java

@@ -8,7 +8,7 @@ public class FnSpecialForm extends SpecialForm {
   }
 
   @Override
-    public Object eval(final Scope parentScope) {
+  public Object eval(final BaseScope parentScope) {
     final ListNode<Node> formalParams = (ListNode<Node>) this.node.rest().first();
     final ListNode<Node> body = this.node.rest().rest();
 

src/main/java/serene/simple/FunctionNode.java

@@ -2,7 +2,7 @@ package serene.simple;
 
 public class FunctionNode extends Node {
     @Override
-    public Object eval(Scope scope) {
+    public Object eval(BaseScope scope) {
         return this;
     }
 

src/main/java/serene/simple/IfSpecialForm.java

@@ -2,7 +2,6 @@ package serene.simple;
 
 
 public class IfSpecialForm extends SpecialForm {
-
   private Node pred;
   private Node ifNode;
   private Node elseNode;
@@ -15,7 +14,7 @@ public class IfSpecialForm extends SpecialForm {
   }
 
   @Override
-    public Object eval(final Scope scope) {
+  public Object eval(final BaseScope scope) {
     Object result = this.pred.eval(scope);
     if (result == null || (result instanceof Boolean && (Boolean) result == false)) {
       return this.elseNode.eval(scope);

src/main/java/serene/simple/ListNode.java

@@ -4,6 +4,9 @@ import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 import java.util.function.Function;
+
+import serene.simple.builtin.AFn;
+
 import static java.util.Arrays.asList;
 
 public class ListNode<T extends Node> extends Node implements Iterable<T> {
@@ -43,14 +46,29 @@ public class ListNode<T extends Node> extends Node implements Iterable<T> {
   }
 
   @Override
-    public Object eval(Scope scope) {
-        Function<Object, Object> f = (Function) this.first().eval(scope);
+  public Object eval(BaseScope scope) {
+    Object f = this.first().eval(scope);
     List<Object> args = new ArrayList<Object>();
 
     for (T node : this.rest()) {
       args.add(node.eval(scope));
     }
-        return f.apply(args.toArray());
+
+    if (f instanceof AFn) {
+      return evalBuiltin(scope, (AFn) f, args);
+    }
+    else {
+      return evalFn(scope, (Function<Object, Object>) f, args);
+    }
+  }
+
+  public Object evalBuiltin(BaseScope scope, AFn fn, List<Object> args) {
+    fn.setArguments(args);
+    return fn.eval(scope);
+  }
+
+  public Object evalFn(BaseScope scope, Function<Object, Object> fn, List<Object> args) {
+    return fn.apply(args.toArray());
   }
 
   public T first() {

src/main/java/serene/simple/Main.java

@@ -19,7 +19,7 @@ public class Main {
   }
 
   private static void startRepl() throws IOException {
-        Scope rootScope = Scope.getRootScope();
+    BaseScope rootScope = new RootScope();
 
     Console console = System.console();
 
@@ -60,7 +60,7 @@ public class Main {
   }
 
   private static void runSerene(String filePath) throws IOException {
-        Scope rootScope = Scope.getRootScope();
+    BaseScope rootScope = new RootScope();
 
     ListNode<Node> nodes = Reader.read(new FileInputStream(filePath));
 

src/main/java/serene/simple/NilNode.java

@@ -4,7 +4,7 @@ public class NilNode extends Node {
     public boolean isTruthy = false;
 
     @Override
-    public Object eval(Scope scope) {
+    public Object eval(BaseScope scope) {
         return null;
     }
 

src/main/java/serene/simple/Node.java

@@ -3,7 +3,7 @@ package serene.simple;
 public abstract class Node {
   public boolean isTruthy = true;
 
-    public abstract Object eval(Scope scope);
+  public abstract Object eval(BaseScope scope);
 
   public boolean equals(Node n) {
     return this == n;

src/main/java/serene/simple/NumberNode.java

@@ -8,7 +8,7 @@ public class NumberNode extends Node {
     }
 
     @Override
-    public Object eval(Scope scope) {
+    public Object eval(BaseScope scope) {
         return this.value;
     }
 

src/main/java/serene/simple/QuoteSpecialForm.java

@@ -1,11 +1,6 @@
 package serene.simple;
 
 public class QuoteSpecialForm extends SpecialForm {
-
-    // public QuoteSpecialForm(Node node) {
-    //     this.x = node;
-    // }
-
   public QuoteSpecialForm(ListNode<Node> node) throws SereneException {
     super(node);
 
@@ -15,7 +10,7 @@ public class QuoteSpecialForm extends SpecialForm {
   }
 
   @Override
-    public Object eval(final Scope scope) {
+  public Object eval(final BaseScope scope) {
     return this.node.rest().first();
   }
 }

src/main/java/serene/simple/RootScope.java

@@ -0,0 +1,42 @@
+package serene.simple;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import serene.simple.builtin.AFn;
+import serene.simple.builtin.PrintlnFn;
+
+public class RootScope extends BaseScope {
+  private final BaseScope parent;
+  private final HashMap<String, Object> symbolsMapping = new HashMap<String, Object>() {{
+      put("println", new PrintlnFn());
+    }};
+    // "+", PlusFn,
+    // "-", MinusFn,
+    // "*", TimesFn,
+    // "/", ObelusFn,
+    // "mod", ModFn,
+    // "now", NowFn,
+
+
+  public RootScope() {
+    this.parent = null;
+    System.out.println(this.symbolsMapping.get("println"));
+
+  }
+
+  @Override
+  public Object lookupSymbol(String symbolName) {
+    if (this.symbolsMapping.containsKey(symbolName)) {
+      return this.symbolsMapping.get(symbolName);
+    }
+    else {
+      throw new RuntimeException(String.format("Variable '%s' is not defined in this scope.",
+                                               symbolName));
+    }
+  }
+
+  public void insertSymbol(String symbolName, Object symbolValue) {
+    this.symbolsMapping.put(symbolName, symbolValue);
+  }
+}

src/main/java/serene/simple/Scope.java

@@ -1,38 +1,14 @@
 package serene.simple;
 
-import java.util.HashMap;
 
-public class Scope {
-    private final HashMap<String, Object> symbolsMapping = new HashMap<String, Object>();
-    private final Scope parent;
-    private static final Scope root = new Scope(null);
+public class Scope extends BaseScope{
+    private final BaseScope parent;
 
     public Scope() {
-        this(null);
+        this(new RootScope());
     }
 
-    public Scope(Scope parent) {
+    public Scope(BaseScope parent) {
         this.parent = parent;
     }
-
-    public Object lookupSymbol(String symbolName) {
-        if (this.symbolsMapping.containsKey(symbolName)) {
-            return this.symbolsMapping.get(symbolName);
-        }
-        else if (this.parent != null) {
-            return this.parent.lookupSymbol(symbolName);
-        }
-        else {
-            throw new RuntimeException(String.format("Variable '%s' is not defined in this scope.",
-                                                     symbolName));
-        }
-    }
-
-    public void insertSymbol(String symbolName, Object symbolValue) {
-        this.symbolsMapping.put(symbolName, symbolValue);
-    }
-
-    public static Scope getRootScope() {
-        return Scope.root;
-    }
 }

src/main/java/serene/simple/SpecialForm.java

@@ -32,7 +32,7 @@ public class SpecialForm extends Node {
   }
 
   @Override
-    public Object eval(Scope scope) throws SereneException {
+  public Object eval(BaseScope scope) throws SereneException {
     throw new SereneException("Can't use SpecialForm directly");
   }
 }

src/main/java/serene/simple/SymbolNode.java

@@ -22,7 +22,7 @@ public class SymbolNode extends Node {
     }
 
     @Override
-    public Object eval(Scope scope) {
+    public Object eval(BaseScope scope) {
         return scope.lookupSymbol(this.name);
     }
 

src/main/java/serene/simple/TrueNode.java

@@ -2,7 +2,7 @@ package serene.simple;
 
 public class TrueNode extends Node {
     @Override
-    public Object eval(Scope scope) {
+    public Object eval(BaseScope scope) {
         return true;
     }
 

src/main/java/serene/simple/builtin/AFn.java

@@ -0,0 +1,31 @@
+package serene.simple.builtin;
+
+import java.util.Collections;
+import java.util.List;
+
+import serene.simple.Node;
+
+
+public abstract class AFn extends Node {
+
+  private List<Object> args;
+
+  public void setArguments() {
+    this.args = Collections.EMPTY_LIST;
+  }
+
+  public void setArguments(List<Object> args) {
+    this.args = args;
+  }
+
+  public List<Object> arguments() {
+    return this.args;
+  }
+
+  public abstract String fnName();
+
+  @Override
+  public String toString() {
+    return String.format("BuiltinFn<%s>", this.fnName());
+  }
+}

src/main/java/serene/simple/builtin/PrintlnFn.java

@@ -0,0 +1,23 @@
+package serene.simple.builtin;
+
+import serene.simple.BaseScope;
+
+
+public class PrintlnFn extends AFn {
+  public String fnName() {
+    return "println";
+  };
+
+  public Object eval(BaseScope scope) {
+    String output = "";
+
+    for(Object x: this.arguments()) {
+      output = String.format(
+        "%s %s", output,
+        (String) x.toString());
+    }
+
+    System.out.println(output);
+    return null;
+  }
+}