diff --git a/zero-compiler/pom.xml b/zero-compiler/pom.xml
index a46968b..6fe08f4 100644
--- a/zero-compiler/pom.xml
+++ b/zero-compiler/pom.xml
@@ -19,6 +19,11 @@
       <artifactId>guava</artifactId>
       <version>11.0.2</version>
     </dependency>
+    <dependency>
+      <groupId>org.functionaljava</groupId>
+      <artifactId>functionaljava</artifactId>
+      <version>3.0</version>
+    </dependency>
   </dependencies>
 
   <build>
diff --git a/zero-compiler/src/main/java/zero/compiler/Main.java b/zero-compiler/src/main/java/zero/compiler/Main.java
index 0b21ea2..c9efd2c 100644
--- a/zero-compiler/src/main/java/zero/compiler/Main.java
+++ b/zero-compiler/src/main/java/zero/compiler/Main.java
@@ -5,8 +5,9 @@
 import java.io.InputStream;
 import java.io.FileInputStream;
 
-import zero.lang.Version;
+import zero.lang.*;
 import zero.compiler.parser.*;
+import zero.interp.ast.*;
 
 public final class Main {
   static final Console C = System.console();
@@ -16,6 +17,8 @@ public final class Main {
   public static void main(final String[] args) throws Exception {
     C.printf(welcome());
 
+    Scope scope = Pervasives.addAll(Scope.EMPTY);
+
     if(args.length > 0) {
       for(final String file : args) {
         final Expression expr = read(new FileInputStream(file));
diff --git a/zero-compiler/src/main/java/zero/compiler/parser/AExpression.java b/zero-compiler/src/main/java/zero/compiler/parser/AExpression.java
new file mode 100644
index 0000000..4b7a2b3
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/compiler/parser/AExpression.java
@@ -0,0 +1,9 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.compiler.parser;
+
+public abstract class AExpression implements Expression {
+  @Override
+  public String toString() {
+    return toString(new StringBuilder()).toString();
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/compiler/parser/ApplyExpression.java b/zero-compiler/src/main/java/zero/compiler/parser/ApplyExpression.java
new file mode 100644
index 0000000..98a5351
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/compiler/parser/ApplyExpression.java
@@ -0,0 +1,30 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.compiler.parser;
+
+public class ApplyExpression extends AExpression {
+  public final Expression fn;
+  public final Expression[] params;
+
+  public ApplyExpression(final Expression fn, final Expression... params) {
+    this.fn = fn;
+    this.params = params == null ? new Expression[0] : params;
+  }
+
+  @Override
+  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
+    return v.visit(this, c);
+  }
+
+  @Override
+  public StringBuilder toString(final StringBuilder b) {
+    b.append("((");
+    fn.toString(b);
+    b.append(')');
+    for(final Expression param : params) {
+      b.append(' ');
+      param.toString(b);
+    }
+    b.append(')');
+    return b;
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/compiler/parser/CaseExpression.java b/zero-compiler/src/main/java/zero/compiler/parser/CaseExpression.java
new file mode 100644
index 0000000..82f2427
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/compiler/parser/CaseExpression.java
@@ -0,0 +1,30 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.compiler.parser;
+
+public class CaseExpression extends AExpression {
+  public final PatternExpression bind;
+  public final Expression result;
+
+  public CaseExpression(final PatternExpression bind, final Expression result) {
+    this.bind = bind;
+    this.result = result;
+  }
+
+  @Override
+  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
+    return v.visit(this, c);
+  }
+
+  @Override
+  public StringBuilder toString(final StringBuilder b) {
+    if(bind.isWildcard()) {
+      b.append("else ");
+    } else {
+      b.append("| ");
+      bind.toString(b);
+      b.append(" -> ");
+    }
+    result.toString(b);
+    return b;
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/compiler/parser/Expression.java b/zero-compiler/src/main/java/zero/compiler/parser/Expression.java
index ebe8671..d6f9f5d 100644
--- a/zero-compiler/src/main/java/zero/compiler/parser/Expression.java
+++ b/zero-compiler/src/main/java/zero/compiler/parser/Expression.java
@@ -5,206 +5,3 @@ public interface Expression {
   <R, C> R accept(ExpressionVisitor<R, C> v, C c);
   StringBuilder toString(StringBuilder b);
 }
-
-abstract class AExpression implements Expression {
-  @Override
-  public String toString() {
-    return toString(new StringBuilder()).toString();
-  }
-}
-
-class NameExpression extends AExpression {
-  final String name;
-
-  public NameExpression(final Token token) {
-    this.name = token.getText();
-  }
-
-  @Override
-  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
-    return v.visit(this, c);
-  }
-
-  @Override
-  public StringBuilder toString(final StringBuilder b) {
-    return b.append(name);
-  }
-}
-
-class IntegerExpression extends AExpression {
-  final int val;
-
-  public IntegerExpression(final Token token) {
-    this.val = Integer.parseInt(token.getText());
-  }
-
-  @Override
-  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
-    return v.visit(this, c);
-  }
-
-  @Override
-  public StringBuilder toString(final StringBuilder b) {
-    return b.append(val);
-  }
-}
-
-class ValDeclExpression extends AExpression {
-  private final NameExpression name;
-  private final Expression val;
-
-  public ValDeclExpression(final NameExpression name, final Expression val) {
-    this.name = name;
-    this.val = val;
-  }
-
-  @Override
-  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
-    return v.visit(this, c);
-  }
-
-  @Override
-  public StringBuilder toString(final StringBuilder b) {
-    b.append("val ");
-    name.toString(b);
-    b.append(" = ");
-    val.toString(b);
-    return b;
-  }
-}
-
-class FnExpression extends AExpression {
-  private final NameExpression[] params;
-  private final Expression body;
-
-  public FnExpression(final Expression body, final NameExpression... params) {
-    this.params = params == null ? new NameExpression[0] : params;
-    this.body = body;
-  }
-
-  @Override
-  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
-    return v.visit(this, c);
-  }
-
-  @Override
-  public StringBuilder toString(final StringBuilder b) {
-    b.append("fn ");
-    for(final NameExpression name : params) {
-      name.toString(b).append(' ');
-    }
-    b.append("-> ");
-    body.toString(b);
-    return b;
-  }
-}
-
-class ApplyExpression extends AExpression {
-  private final Expression fn;
-  private final Expression[] params;
-
-  public ApplyExpression(final Expression fn, final Expression... params) {
-    this.fn = fn;
-    this.params = params == null ? new Expression[0] : params;
-  }
-
-  @Override
-  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
-    return v.visit(this, c);
-  }
-
-  @Override
-  public StringBuilder toString(final StringBuilder b) {
-    b.append("((");
-    fn.toString(b);
-    b.append(')');
-    for(final Expression param : params) {
-      b.append(' ');
-      param.toString(b);
-    }
-    b.append(')');
-    return b;
-  }
-}
-
-class MatchExpression extends AExpression {
-  private final Expression val;
-  private final CaseExpression[] cases;
-
-  public MatchExpression(final Expression val, final CaseExpression... cases) {
-    this.val = val;
-    this.cases = cases == null ? new CaseExpression[0] : cases;
-  }
-
-  @Override
-  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
-    return v.visit(this, c);
-  }
-
-  @Override
-  public StringBuilder toString(final StringBuilder b) {
-    b.append("match ");
-    val.toString(b);
-    b.append(" with ");
-    for(final CaseExpression c : cases) {
-      c.toString(b);
-      b.append(' ');
-    }
-    b.append("end");
-    return b;
-  }
-}
-
-class CaseExpression extends AExpression {
-  private final PatternExpression bind;
-  private final Expression result;
-
-  public CaseExpression(final PatternExpression bind, final Expression result) {
-    this.bind = bind;
-    this.result = result;
-  }
-
-  @Override
-  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
-    return v.visit(this, c);
-  }
-
-  @Override
-  public StringBuilder toString(final StringBuilder b) {
-    if(bind.isWildcard()) {
-      b.append("else ");
-    } else {
-      b.append("| ");
-      bind.toString(b);
-      b.append(" -> ");
-    }
-    result.toString(b);
-    return b;
-  }
-}
-
-class PatternExpression extends AExpression {
-  public static final PatternExpression WILDCARD = new PatternExpression(new NameExpression(new Token(Token.Type.NAME, "_")));
-
-  private final Expression pattern;
-
-  public PatternExpression(final Expression pattern) {
-    this.pattern = pattern;
-  }
-
-  @Override
-  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
-    return v.visit(this, c);
-  }
-
-  @Override
-  public StringBuilder toString(final StringBuilder b) {
-    pattern.toString(b);
-    return b;
-  }
-
-  public boolean isWildcard() {
-    return pattern.getClass() == NameExpression.class
-      && ((NameExpression) pattern).name.equals("_");
-  }
-}
diff --git a/zero-compiler/src/main/java/zero/compiler/parser/FnExpression.java b/zero-compiler/src/main/java/zero/compiler/parser/FnExpression.java
new file mode 100644
index 0000000..3f6a348
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/compiler/parser/FnExpression.java
@@ -0,0 +1,28 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.compiler.parser;
+
+public class FnExpression extends AExpression {
+  public final NameExpression[] params;
+  public final Expression body;
+
+  public FnExpression(final Expression body, final NameExpression... params) {
+    this.params = params == null ? new NameExpression[0] : params;
+    this.body = body;
+  }
+
+  @Override
+  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
+    return v.visit(this, c);
+  }
+
+  @Override
+  public StringBuilder toString(final StringBuilder b) {
+    b.append("fn ");
+    for(final NameExpression name : params) {
+      name.toString(b).append(' ');
+    }
+    b.append("-> ");
+    body.toString(b);
+    return b;
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/compiler/parser/IntegerExpression.java b/zero-compiler/src/main/java/zero/compiler/parser/IntegerExpression.java
new file mode 100644
index 0000000..cd78a53
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/compiler/parser/IntegerExpression.java
@@ -0,0 +1,20 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.compiler.parser;
+
+public class IntegerExpression extends AExpression {
+  public final int val;
+
+  public IntegerExpression(final Token token) {
+    this.val = Integer.parseInt(token.getText());
+  }
+
+  @Override
+  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
+    return v.visit(this, c);
+  }
+
+  @Override
+  public StringBuilder toString(final StringBuilder b) {
+    return b.append(val);
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/compiler/parser/MatchExpression.java b/zero-compiler/src/main/java/zero/compiler/parser/MatchExpression.java
new file mode 100644
index 0000000..2438251
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/compiler/parser/MatchExpression.java
@@ -0,0 +1,30 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.compiler.parser;
+
+public class MatchExpression extends AExpression {
+  public final Expression val;
+  public final CaseExpression[] cases;
+
+  public MatchExpression(final Expression val, final CaseExpression... cases) {
+    this.val = val;
+    this.cases = cases == null ? new CaseExpression[0] : cases;
+  }
+
+  @Override
+  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
+    return v.visit(this, c);
+  }
+
+  @Override
+  public StringBuilder toString(final StringBuilder b) {
+    b.append("match ");
+    val.toString(b);
+    b.append(" with ");
+    for(final CaseExpression c : cases) {
+      c.toString(b);
+      b.append(' ');
+    }
+    b.append("end");
+    return b;
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/compiler/parser/NameExpression.java b/zero-compiler/src/main/java/zero/compiler/parser/NameExpression.java
new file mode 100644
index 0000000..f9b5f23
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/compiler/parser/NameExpression.java
@@ -0,0 +1,20 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.compiler.parser;
+
+public class NameExpression extends AExpression {
+  public final String name;
+
+  public NameExpression(final Token token) {
+    this.name = token.getText();
+  }
+
+  @Override
+  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
+    return v.visit(this, c);
+  }
+
+  @Override
+  public StringBuilder toString(final StringBuilder b) {
+    return b.append(name);
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/compiler/parser/PatternExpression.java b/zero-compiler/src/main/java/zero/compiler/parser/PatternExpression.java
new file mode 100644
index 0000000..038b89a
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/compiler/parser/PatternExpression.java
@@ -0,0 +1,28 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.compiler.parser;
+
+public class PatternExpression extends AExpression {
+  public static final PatternExpression WILDCARD = new PatternExpression(new NameExpression(new Token(Token.Type.NAME, "_")));
+
+  public final Expression pattern;
+
+  public PatternExpression(final Expression pattern) {
+    this.pattern = pattern;
+  }
+
+  @Override
+  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
+    return v.visit(this, c);
+  }
+
+  @Override
+  public StringBuilder toString(final StringBuilder b) {
+    pattern.toString(b);
+    return b;
+  }
+
+  public boolean isWildcard() {
+    return pattern.getClass() == NameExpression.class
+      && ((NameExpression) pattern).name.equals("_");
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/compiler/parser/ValDeclExpression.java b/zero-compiler/src/main/java/zero/compiler/parser/ValDeclExpression.java
new file mode 100644
index 0000000..2455b2d
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/compiler/parser/ValDeclExpression.java
@@ -0,0 +1,26 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.compiler.parser;
+
+public class ValDeclExpression extends AExpression {
+  public final NameExpression name;
+  public final Expression val;
+
+  public ValDeclExpression(final NameExpression name, final Expression val) {
+    this.name = name;
+    this.val = val;
+  }
+
+  @Override
+  public <R, C> R accept(ExpressionVisitor<R, C> v, C c) {
+    return v.visit(this, c);
+  }
+
+  @Override
+  public StringBuilder toString(final StringBuilder b) {
+    b.append("val ");
+    name.toString(b);
+    b.append(" = ");
+    val.toString(b);
+    return b;
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/interp/ast/Interpreter.java b/zero-compiler/src/main/java/zero/interp/ast/Interpreter.java
index d4c37e3..b34a2d4 100644
--- a/zero-compiler/src/main/java/zero/interp/ast/Interpreter.java
+++ b/zero-compiler/src/main/java/zero/interp/ast/Interpreter.java
@@ -1,24 +1,60 @@
 /* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
 package zero.interp.ast;
 
+import zero.lang.*;
 import zero.compiler.parser.*;
 
 import java.util.Map;
 
 public class Interpreter {
-  // with pervasives
-  // without
-
-  Result eval(Expression e, Scope in) {
+  public Result eval(final Expression e, final Scope in) {
     return null;
   }
 }
 
-class Scope {
-  Map<String, ?> defs;
-}
+class AstWalk implements ExpressionVisitor<Result, Scope>  {
+  @Override
+  public Result visit(NameExpression expr, Scope scope) {
+    return new Result(scope.get(expr.name), scope);
+  }
+
+  @Override
+  public Result visit(IntegerExpression expr, Scope scope) {
+    return new Result(new Val(expr.val), scope);
+  }
+
+  @Override
+  public Result visit(ValDeclExpression expr, Scope scope) {
+    scope = scope.add(expr.name, new Val(expr.val));
+    return new Result(scope);
+  }
+
+  @Override
+  public Result visit(FnExpression expr, Scope scope) {
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public Result visit(ApplyExpression expr, Scope scope) {
 
-class Result {
-  Expression val;
-  Scope updated;
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public Result visit(MatchExpression expr, Scope scope) {
+
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public Result visit(CaseExpression expr, Scope scope) {
+
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public Result visit(PatternExpression expr, Scope scope) {
+
+    throw new UnsupportedOperationException();
+  }
 }
\ No newline at end of file
diff --git a/zero-compiler/src/main/java/zero/interp/ast/Result.java b/zero-compiler/src/main/java/zero/interp/ast/Result.java
new file mode 100644
index 0000000..f1c7850
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/interp/ast/Result.java
@@ -0,0 +1,25 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.interp.ast;
+
+import zero.lang.*;
+import zero.compiler.parser.*;
+
+import java.util.Map;
+
+public class Result {
+  public final Val val;
+  public final Scope newScope;
+
+  public Result(final Val val) {
+    this(val, null);
+  }
+
+  public Result(final Scope newScope) {
+    this(null, newScope);
+  }
+
+  public Result(final Val val, final Scope newScope) {
+    this.val = val;
+    this.newScope = newScope;
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/interp/ast/Scope.java b/zero-compiler/src/main/java/zero/interp/ast/Scope.java
new file mode 100644
index 0000000..e09900a
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/interp/ast/Scope.java
@@ -0,0 +1,26 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.interp.ast;
+
+import zero.lang.*;
+import zero.compiler.parser.*;
+import zero.util.*;
+
+import java.util.Map;
+
+public class Scope {
+  public static final Scope EMPTY = new Scope(Nil.<String, Val>get());
+
+  private final Associative<String, Val> defs;
+
+  private Scope(final Associative<String, Val> defs) {
+    this.defs = defs;
+  }
+
+  public Scope add(final String name, final Val val) {
+    return new Scope(defs.add(name, val));
+  }
+
+  public Val get(final String name) {
+    return defs.get(name);
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/lang/Fn0.java b/zero-compiler/src/main/java/zero/lang/Fn0.java
new file mode 100644
index 0000000..60bb2d1
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/lang/Fn0.java
@@ -0,0 +1,6 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.lang;
+
+public interface Fn0<R> {
+  R apply();
+}
diff --git a/zero-compiler/src/main/java/zero/lang/Fn1.java b/zero-compiler/src/main/java/zero/lang/Fn1.java
new file mode 100644
index 0000000..2d7b658
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/lang/Fn1.java
@@ -0,0 +1,6 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.lang;
+
+public interface Fn1<R, A> {
+  R apply(A a);
+}
diff --git a/zero-compiler/src/main/java/zero/lang/Fn2.java b/zero-compiler/src/main/java/zero/lang/Fn2.java
new file mode 100644
index 0000000..2520107
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/lang/Fn2.java
@@ -0,0 +1,6 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.lang;
+
+public interface Fn2<R, A, B> {
+  R apply(A a, B b);
+}
diff --git a/zero-compiler/src/main/java/zero/lang/Pervasives.java b/zero-compiler/src/main/java/zero/lang/Pervasives.java
index dbdfde3..8f5750c 100644
--- a/zero-compiler/src/main/java/zero/lang/Pervasives.java
+++ b/zero-compiler/src/main/java/zero/lang/Pervasives.java
@@ -1,7 +1,31 @@
 /* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
 package zero.lang;
 
+import zero.interp.ast.Scope;
+
 public final class Pervasives {
-  // + - *
+  public static final Val plus = new Val(new Fn2<Integer, Integer, Integer>() {
+    @Override
+    public Integer apply(final Integer a, final Integer b) {
+      return a + b;
+    }
+  });
+  public static final Val minus = new Val(new Fn2<Integer, Integer, Integer>() {
+    @Override
+    public Integer apply(final Integer a, final Integer b) {
+      return a - b;
+    }
+  });
+  public static final Val times = new Val(new Fn2<Integer, Integer, Integer>() {
+    @Override
+    public Integer apply(final Integer a, final Integer b) {
+      return a * b;
+    }
+  });
+
+  public static Scope addAll(final Scope scope) {
+    return scope.add("+", plus).add("-", minus).add("*", times);
+  }
+
   private Pervasives() {}
-}
\ No newline at end of file
+}
diff --git a/zero-compiler/src/main/java/zero/lang/Val.java b/zero-compiler/src/main/java/zero/lang/Val.java
new file mode 100644
index 0000000..21eb84c
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/lang/Val.java
@@ -0,0 +1,24 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.lang;
+
+import zero.compiler.parser.Expression;
+
+public class Val {
+  final Object val;
+
+  public Val(final Object val) {
+    this.val = val;
+  }
+
+  public Fn2 asFn2() {
+    return (Fn2) val;
+  }
+
+  public Integer asInteger() {
+    return (Integer) val;
+  }
+
+  public Expression asExpression() {
+    return (Expression) val;
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/util/Associative.java b/zero-compiler/src/main/java/zero/util/Associative.java
new file mode 100644
index 0000000..9ac27d4
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/util/Associative.java
@@ -0,0 +1,7 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.util;
+
+public interface Associative<K, V> {
+  Associative add(K k, V v);
+  V get(K k);
+}
diff --git a/zero-compiler/src/main/java/zero/util/AssociativeList.java b/zero-compiler/src/main/java/zero/util/AssociativeList.java
new file mode 100644
index 0000000..0c1ae22
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/util/AssociativeList.java
@@ -0,0 +1,26 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.util;
+
+public class AssociativeList<K, V> implements Associative<K, V> {
+  private final K k;
+  private final V v;
+  private final Associative<K, V> tl;
+
+  public AssociativeList(final K k, final V v, final Associative<K, V> tl) {
+    this.k = k;
+    this.v = v;
+    this.tl = tl;
+  }
+
+  public Associative add(K k, V v) {
+    return new AssociativeList<>(k, v, this);
+  }
+
+  public V get(K k) {
+    if(k.equals(this.k)) {
+      return v;
+    } else {
+      return tl.get(k);
+    }
+  }
+}
diff --git a/zero-compiler/src/main/java/zero/util/Nil.java b/zero-compiler/src/main/java/zero/util/Nil.java
new file mode 100644
index 0000000..2c43c72
--- /dev/null
+++ b/zero-compiler/src/main/java/zero/util/Nil.java
@@ -0,0 +1,19 @@
+/* Copyright (C) 2012 Matt O'Connor <thegreendragon@gmail.com> */
+package zero.util;
+
+public class Nil<K, V> implements Associative<K, V> {
+  private static final Associative<?, ?> NIL = new Nil<>();
+  private Nil() {}
+
+  public static <K, V> Associative<K, V> get() {
+    return (Associative<K, V>) NIL;
+  }
+
+  public Associative add(K k, V v) {
+    return new AssociativeList<>(k, v, this);
+  }
+
+  public V get(K k) {
+    return null;
+  }
+}