Split interpreter values from primitives

23 files changed, 321 insertions, 138 deletions

diff --git a/src/main/java/org/zwobble/couscous/JavaProject.java b/src/main/java/org/zwobble/couscous/JavaProject.java
index a13399c..04ed53d 100644
--- a/src/main/java/org/zwobble/couscous/JavaProject.java
+++ b/src/main/java/org/zwobble/couscous/JavaProject.java
@@ -1,10 +1,10 @@
 package org.zwobble.couscous;
 
-import org.zwobble.couscous.interpreter.values.IntegerValue;
+import org.zwobble.couscous.interpreter.values.IntegerInterpreterValue;
 
 public class JavaProject {
     public static MapBackedProject.Builder builder() {
         return MapBackedProject.builder()
-            .addClass(IntegerValue.TYPE);
+            .addClass(IntegerInterpreterValue.TYPE);
     }
 }
diff --git a/src/main/java/org/zwobble/couscous/ast/LiteralNode.java b/src/main/java/org/zwobble/couscous/ast/LiteralNode.java
index 6bc498a..05a599c 100644
--- a/src/main/java/org/zwobble/couscous/ast/LiteralNode.java
+++ b/src/main/java/org/zwobble/couscous/ast/LiteralNode.java
@@ -1,32 +1,31 @@
 package org.zwobble.couscous.ast;
 
 import org.zwobble.couscous.ast.visitors.ExpressionNodeVisitor;
-import org.zwobble.couscous.interpreter.values.BooleanValue;
-import org.zwobble.couscous.interpreter.values.IntegerValue;
-import org.zwobble.couscous.interpreter.values.InterpreterValue;
-import org.zwobble.couscous.interpreter.values.StringValue;
+import org.zwobble.couscous.values.PrimitiveValue;
+
+import static org.zwobble.couscous.values.PrimitiveValues.value;
 
 import lombok.Value;
 
 @Value
 public class LiteralNode implements ExpressionNode {
-    public static LiteralNode literal(InterpreterValue value) {
+    public static LiteralNode literal(PrimitiveValue value) {
         return new LiteralNode(value);
     }
     
     public static LiteralNode literal(String value) {
-        return new LiteralNode(new StringValue(value));
+        return new LiteralNode(value(value));
     }
     
     public static LiteralNode literal(int value) {
-        return new LiteralNode(new IntegerValue(value));
+        return new LiteralNode(value(value));
     }
     
     public static LiteralNode literal(boolean value) {
-        return new LiteralNode(new BooleanValue(value));
+        return new LiteralNode(value(value));
     }
     
-    InterpreterValue value;
+    PrimitiveValue value;
 
     @Override
     public <T> T accept(ExpressionNodeVisitor<T> visitor) {
diff --git a/src/main/java/org/zwobble/couscous/backends/python/PythonCodeGenerator.java b/src/main/java/org/zwobble/couscous/backends/python/PythonCodeGenerator.java
index 4c26a0a..eae713c 100644
--- a/src/main/java/org/zwobble/couscous/backends/python/PythonCodeGenerator.java
+++ b/src/main/java/org/zwobble/couscous/backends/python/PythonCodeGenerator.java
@@ -21,8 +21,11 @@ import org.zwobble.couscous.backends.python.ast.PythonExpressionNode;
 import org.zwobble.couscous.backends.python.ast.PythonFunctionDefinitionNode;
 import org.zwobble.couscous.backends.python.ast.PythonModuleNode;
 import org.zwobble.couscous.backends.python.ast.PythonStatementNode;
-import org.zwobble.couscous.interpreter.values.IntegerValue;
-import org.zwobble.couscous.interpreter.values.StringValue;
+import org.zwobble.couscous.values.BooleanValue;
+import org.zwobble.couscous.values.IntegerValue;
+import org.zwobble.couscous.values.PrimitiveValueVisitor;
+import org.zwobble.couscous.values.StringValue;
+import org.zwobble.couscous.values.UnitValue;
 
 import static java.util.Arrays.asList;
 import static org.zwobble.couscous.backends.python.ast.PythonClassNode.pythonClass;
@@ -81,14 +84,27 @@ public class PythonCodeGenerator {
     private static class ExpressionGenerator implements ExpressionNodeVisitor<PythonExpressionNode> {
         @Override
         public PythonExpressionNode visit(LiteralNode literal) {
-            // TODO: use visitor
-            if (literal.getValue() instanceof IntegerValue) {
-                return pythonIntegerLiteral(((IntegerValue)literal.getValue()).getValue());
-            } else if (literal.getValue() instanceof StringValue) {
-                    return pythonStringLiteral(((StringValue)literal.getValue()).getValue());
-            } else {
-                throw new UnsupportedOperationException();
-            }
+            return literal.getValue().accept(new PrimitiveValueVisitor<PythonExpressionNode>() {
+                @Override
+                public PythonExpressionNode visit(IntegerValue value) {
+                    return pythonIntegerLiteral(value.getValue());
+                }
+
+                @Override
+                public PythonExpressionNode visit(StringValue value) {
+                    return pythonStringLiteral(value.getValue());
+                }
+
+                @Override
+                public PythonExpressionNode visit(BooleanValue value) {
+                    throw new UnsupportedOperationException();
+                }
+
+                @Override
+                public PythonExpressionNode visit(UnitValue unitValue) {
+                    throw new UnsupportedOperationException();
+                }
+            });
         }
 
         @Override
diff --git a/src/main/java/org/zwobble/couscous/interpreter/Evaluator.java b/src/main/java/org/zwobble/couscous/interpreter/Evaluator.java
index 6b61b7f..9362698 100644
--- a/src/main/java/org/zwobble/couscous/interpreter/Evaluator.java
+++ b/src/main/java/org/zwobble/couscous/interpreter/Evaluator.java
@@ -11,8 +11,9 @@ import org.zwobble.couscous.ast.StaticMethodCallNode;
 import org.zwobble.couscous.ast.TernaryConditionalNode;
 import org.zwobble.couscous.ast.VariableReferenceNode;
 import org.zwobble.couscous.ast.visitors.ExpressionNodeVisitor;
-import org.zwobble.couscous.interpreter.values.BooleanValue;
+import org.zwobble.couscous.interpreter.values.BooleanInterpreterValue;
 import org.zwobble.couscous.interpreter.values.InterpreterValue;
+import org.zwobble.couscous.interpreter.values.InterpreterValues;
 
 import lombok.val;
 
@@ -33,7 +34,7 @@ public class Evaluator implements ExpressionNodeVisitor<InterpreterValue> {
 
     @Override
     public InterpreterValue visit(LiteralNode literal) {
-        return literal.getValue();
+        return InterpreterValues.value(literal.getValue());
     }
 
     @Override
@@ -51,10 +52,10 @@ public class Evaluator implements ExpressionNodeVisitor<InterpreterValue> {
     @Override
     public InterpreterValue visit(TernaryConditionalNode ternaryConditional) {
         val condition = eval(ternaryConditional.getCondition());
-        if (!(condition instanceof BooleanValue)) {
+        if (!(condition instanceof BooleanInterpreterValue)) {
             throw new ConditionMustBeBoolean(condition);
         }
-        val branch = ((BooleanValue)condition).getValue()
+        val branch = ((BooleanInterpreterValue)condition).getValue()
             ? ternaryConditional.getIfTrue()
             : ternaryConditional.getIfFalse();
         return eval(branch);
diff --git a/src/main/java/org/zwobble/couscous/interpreter/Executor.java b/src/main/java/org/zwobble/couscous/interpreter/Executor.java
index 2f12e0c..4ed4a04 100644
--- a/src/main/java/org/zwobble/couscous/interpreter/Executor.java
+++ b/src/main/java/org/zwobble/couscous/interpreter/Executor.java
@@ -12,7 +12,7 @@ import org.zwobble.couscous.ast.StatementNode;
 import org.zwobble.couscous.ast.VariableNode;
 import org.zwobble.couscous.ast.visitors.StatementNodeVisitor;
 import org.zwobble.couscous.interpreter.values.InterpreterValue;
-import org.zwobble.couscous.interpreter.values.UnitValue;
+import org.zwobble.couscous.interpreter.values.UnitInterpreterValue;
 
 import static org.zwobble.couscous.interpreter.Evaluator.eval;
 
@@ -28,7 +28,7 @@ public class Executor implements StatementNodeVisitor<Optional<InterpreterValue>
                 return result.get();
             }
         }
-        return UnitValue.UNIT;
+        return UnitInterpreterValue.UNIT;
     }
 
     private static Environment buildEnvironment(
diff --git a/src/main/java/org/zwobble/couscous/interpreter/Interpreter.java b/src/main/java/org/zwobble/couscous/interpreter/Interpreter.java
index 39191ce..0c36d91 100644
--- a/src/main/java/org/zwobble/couscous/interpreter/Interpreter.java
+++ b/src/main/java/org/zwobble/couscous/interpreter/Interpreter.java
@@ -5,11 +5,11 @@ import java.util.stream.Collectors;
 
 import org.zwobble.couscous.Project;
 import org.zwobble.couscous.ast.ExpressionNode;
-import org.zwobble.couscous.ast.LiteralNode;
 import org.zwobble.couscous.interpreter.values.InterpreterValue;
 
 import com.google.common.collect.ImmutableMap;
 
+import static org.zwobble.couscous.ast.LiteralNode.literal;
 import static org.zwobble.couscous.ast.StaticMethodCallNode.staticMethodCall;
 import static org.zwobble.couscous.interpreter.Evaluator.eval;
 
@@ -25,7 +25,7 @@ public class Interpreter {
     public InterpreterValue run(String className, String methodName, List<InterpreterValue> arguments) {
         val argumentExpressions = arguments
             .stream()
-            .<ExpressionNode>map(LiteralNode::literal)
+            .<ExpressionNode>map(argument -> literal(argument.toPrimitiveValue().get()))
             .collect(Collectors.toList());
         return eval(new Environment(project, ImmutableMap.of()),
             staticMethodCall(className, methodName, argumentExpressions));
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/BooleanInterpreterValue.java b/src/main/java/org/zwobble/couscous/interpreter/values/BooleanInterpreterValue.java
new file mode 100644
index 0000000..4ab2d18
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/interpreter/values/BooleanInterpreterValue.java
@@ -0,0 +1,33 @@
+package org.zwobble.couscous.interpreter.values;
+
+import java.util.Optional;
+
+import org.zwobble.couscous.values.PrimitiveValue;
+import org.zwobble.couscous.values.PrimitiveValues;
+
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.Value;
+
+@Value
+public class BooleanInterpreterValue implements InterpreterValue {
+    private static final ConcreteType<BooleanInterpreterValue> TYPE = ConcreteType.<BooleanInterpreterValue>builder("Boolean")
+        .build();
+    
+    @Getter(value = AccessLevel.NONE)
+    boolean value;
+
+    public boolean getValue() {
+        return value;
+    }
+
+    @Override
+    public ConcreteType<?> getType() {
+        return TYPE;
+    }
+
+    @Override
+    public Optional<PrimitiveValue> toPrimitiveValue() {
+        return Optional.of(PrimitiveValues.value(value));
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/BooleanValue.java b/src/main/java/org/zwobble/couscous/interpreter/values/BooleanValue.java
deleted file mode 100644
index 1837d6f..0000000
--- a/src/main/java/org/zwobble/couscous/interpreter/values/BooleanValue.java
+++ /dev/null
@@ -1,23 +0,0 @@
-package org.zwobble.couscous.interpreter.values;
-
-import lombok.AccessLevel;
-import lombok.Getter;
-import lombok.Value;
-
-@Value
-public class BooleanValue implements InterpreterValue {
-    private static final ConcreteType<BooleanValue> TYPE = ConcreteType.<BooleanValue>builder("Boolean")
-        .build();
-    
-    @Getter(value = AccessLevel.NONE)
-    boolean value;
-
-    public boolean getValue() {
-        return value;
-    }
-
-    @Override
-    public ConcreteType<?> getType() {
-        return TYPE;
-    }
-}
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/IntegerInterpreterValue.java b/src/main/java/org/zwobble/couscous/interpreter/values/IntegerInterpreterValue.java
new file mode 100644
index 0000000..c7d7be3
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/interpreter/values/IntegerInterpreterValue.java
@@ -0,0 +1,37 @@
+package org.zwobble.couscous.interpreter.values;
+
+import java.util.Optional;
+
+import org.zwobble.couscous.values.IntegerValue;
+import org.zwobble.couscous.values.PrimitiveValue;
+import org.zwobble.couscous.values.PrimitiveValues;
+import org.zwobble.couscous.values.StringValue;
+
+import static java.util.Arrays.asList;
+
+import lombok.Value;
+import lombok.val;
+
+@Value
+public class IntegerInterpreterValue implements InterpreterValue {
+    public static final ConcreteType<?> TYPE = ConcreteType.<IntegerInterpreterValue>builder(IntegerValue.REF)
+        .staticMethod("parseInt", asList(StringValue.REF),
+            (environment, arguments) -> {
+                val value = (StringInterpreterValue)arguments.get(0);
+                return new IntegerInterpreterValue(Integer.parseInt(value.getValue()));
+            })
+        
+        .build();
+    
+    int value;
+
+    @Override
+    public ConcreteType<?> getType() {
+        return TYPE;
+    }
+
+    @Override
+    public Optional<PrimitiveValue> toPrimitiveValue() {
+        return Optional.of(PrimitiveValues.value(value));
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/IntegerValue.java b/src/main/java/org/zwobble/couscous/interpreter/values/IntegerValue.java
deleted file mode 100644
index 89fd056..0000000
--- a/src/main/java/org/zwobble/couscous/interpreter/values/IntegerValue.java
+++ /dev/null
@@ -1,30 +0,0 @@
-package org.zwobble.couscous.interpreter.values;
-
-import org.zwobble.couscous.values.TypeReference;
-
-import static java.util.Arrays.asList;
-import static org.zwobble.couscous.values.TypeReference.typeRef;
-
-import lombok.Value;
-import lombok.val;
-
-@Value
-public class IntegerValue implements InterpreterValue {
-    public static final TypeReference REF = typeRef("java.lang.Integer");
-    
-    public static final ConcreteType<?> TYPE = ConcreteType.<IntegerValue>builder(REF)
-        .staticMethod("parseInt", asList(StringValue.REF),
-            (environment, arguments) -> {
-                val value = (StringValue)arguments.get(0);
-                return new IntegerValue(Integer.parseInt(value.getValue()));
-            })
-        
-        .build();
-    
-    int value;
-
-    @Override
-    public ConcreteType<?> getType() {
-        return TYPE;
-    }
-}
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/InterpreterValue.java b/src/main/java/org/zwobble/couscous/interpreter/values/InterpreterValue.java
index cf2aa5b..7696ff2 100644
--- a/src/main/java/org/zwobble/couscous/interpreter/values/InterpreterValue.java
+++ b/src/main/java/org/zwobble/couscous/interpreter/values/InterpreterValue.java
@@ -1,5 +1,10 @@
 package org.zwobble.couscous.interpreter.values;
 
+import java.util.Optional;
+
+import org.zwobble.couscous.values.PrimitiveValue;
+
 public interface InterpreterValue {
     ConcreteType<?> getType();
+    Optional<PrimitiveValue> toPrimitiveValue();
 }
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/InterpreterValues.java b/src/main/java/org/zwobble/couscous/interpreter/values/InterpreterValues.java
index ec2d97f..37a0669 100644
--- a/src/main/java/org/zwobble/couscous/interpreter/values/InterpreterValues.java
+++ b/src/main/java/org/zwobble/couscous/interpreter/values/InterpreterValues.java
@@ -1,13 +1,44 @@
 package org.zwobble.couscous.interpreter.values;
 
+import org.zwobble.couscous.values.BooleanValue;
+import org.zwobble.couscous.values.IntegerValue;
+import org.zwobble.couscous.values.PrimitiveValue;
+import org.zwobble.couscous.values.PrimitiveValueVisitor;
+import org.zwobble.couscous.values.StringValue;
+import org.zwobble.couscous.values.UnitValue;
+
 public class InterpreterValues {
-    public static final UnitValue UNIT = UnitValue.UNIT;
+    public static final UnitInterpreterValue UNIT = UnitInterpreterValue.UNIT;
     
     public static InterpreterValue value(int value) {
-        return new IntegerValue(value);
+        return new IntegerInterpreterValue(value);
     }
     
     public static InterpreterValue value(String value) {
-        return new StringValue(value);
+        return new StringInterpreterValue(value);
+    }
+
+    public static InterpreterValue value(PrimitiveValue value) {
+        return value.accept(new PrimitiveValueVisitor<InterpreterValue>() {
+            @Override
+            public InterpreterValue visit(IntegerValue value) {
+                return new IntegerInterpreterValue(value.getValue());
+            }
+
+            @Override
+            public InterpreterValue visit(StringValue value) {
+                return new StringInterpreterValue(value.getValue());
+            }
+
+            @Override
+            public InterpreterValue visit(BooleanValue value) {
+                return new BooleanInterpreterValue(value.getValue());
+            }
+
+            @Override
+            public InterpreterValue visit(UnitValue unitValue) {
+                return UNIT;
+            }
+        });
     }
 }
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/StringInterpreterValue.java b/src/main/java/org/zwobble/couscous/interpreter/values/StringInterpreterValue.java
new file mode 100644
index 0000000..f17cdd5
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/interpreter/values/StringInterpreterValue.java
@@ -0,0 +1,41 @@
+package org.zwobble.couscous.interpreter.values;
+
+import java.util.Optional;
+
+import org.zwobble.couscous.values.IntegerValue;
+import org.zwobble.couscous.values.PrimitiveValue;
+import org.zwobble.couscous.values.PrimitiveValues;
+import org.zwobble.couscous.values.StringValue;
+
+import static java.util.Arrays.asList;
+
+import lombok.Value;
+import lombok.val;
+
+@Value
+public class StringInterpreterValue implements InterpreterValue {
+    public static final ConcreteType<?> TYPE = ConcreteType.<StringInterpreterValue>builder(StringValue.REF)
+        .method("length", asList(),
+            (receiver, arguments) -> new IntegerInterpreterValue(receiver.value.length()))
+        
+        .method("substring", asList(IntegerValue.REF, IntegerValue.REF),
+            (receiver, arguments) -> {
+                val startIndex = (IntegerInterpreterValue)arguments.get(0);
+                val endIndex = (IntegerInterpreterValue)arguments.get(1);
+                return new StringInterpreterValue(receiver.value.substring(startIndex.getValue(), endIndex.getValue()));
+            })
+        
+        .build();
+    
+    String value;
+
+    @Override
+    public ConcreteType<?> getType() {
+        return TYPE;
+    }
+
+    @Override
+    public Optional<PrimitiveValue> toPrimitiveValue() {
+        return Optional.of(PrimitiveValues.value(value));
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/StringValue.java b/src/main/java/org/zwobble/couscous/interpreter/values/StringValue.java
deleted file mode 100644
index 43a4bde..0000000
--- a/src/main/java/org/zwobble/couscous/interpreter/values/StringValue.java
+++ /dev/null
@@ -1,34 +0,0 @@
-package org.zwobble.couscous.interpreter.values;
-
-import org.zwobble.couscous.values.TypeReference;
-
-import static java.util.Arrays.asList;
-import static org.zwobble.couscous.values.TypeReference.typeRef;
-
-import lombok.Value;
-import lombok.val;
-
-@Value
-public class StringValue implements InterpreterValue {
-    public static final TypeReference REF = typeRef("java.lang.String");
-    
-    public static final ConcreteType<?> TYPE = ConcreteType.<StringValue>builder(REF)
-        .method("length", asList(),
-            (receiver, arguments) -> new IntegerValue(receiver.value.length()))
-        
-        .method("substring", asList(IntegerValue.REF, IntegerValue.REF),
-            (receiver, arguments) -> {
-                val startIndex = (IntegerValue)arguments.get(0);
-                val endIndex = (IntegerValue)arguments.get(1);
-                return new StringValue(receiver.value.substring(startIndex.getValue(), endIndex.getValue()));
-            })
-        
-        .build();
-    
-    String value;
-
-    @Override
-    public ConcreteType<?> getType() {
-        return TYPE;
-    }
-}
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/UnitInterpreterValue.java b/src/main/java/org/zwobble/couscous/interpreter/values/UnitInterpreterValue.java
new file mode 100644
index 0000000..e34882b
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/interpreter/values/UnitInterpreterValue.java
@@ -0,0 +1,29 @@
+package org.zwobble.couscous.interpreter.values;
+
+import java.util.Optional;
+
+import org.zwobble.couscous.values.PrimitiveValue;
+import org.zwobble.couscous.values.PrimitiveValues;
+
+import lombok.ToString;
+
+@ToString
+public class UnitInterpreterValue implements InterpreterValue {
+    private static final ConcreteType<?> TYPE = ConcreteType.<UnitInterpreterValue>builder("Unit")
+        .build();
+    
+    public static final UnitInterpreterValue UNIT = new UnitInterpreterValue(); 
+    
+    private UnitInterpreterValue() {
+    }
+
+    @Override
+    public ConcreteType<?> getType() {
+        return TYPE;
+    }
+
+    @Override
+    public Optional<PrimitiveValue> toPrimitiveValue() {
+        return Optional.of(PrimitiveValues.UNIT);
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/UnitValue.java b/src/main/java/org/zwobble/couscous/interpreter/values/UnitValue.java
deleted file mode 100644
index 4e2eb2c..0000000
--- a/src/main/java/org/zwobble/couscous/interpreter/values/UnitValue.java
+++ /dev/null
@@ -1,19 +0,0 @@
-package org.zwobble.couscous.interpreter.values;
-
-import lombok.ToString;
-
-@ToString
-public class UnitValue implements InterpreterValue {
-    private static final ConcreteType<?> TYPE = ConcreteType.<UnitValue>builder("Unit")
-        .build();
-    
-    public static final UnitValue UNIT = new UnitValue(); 
-    
-    private UnitValue() {
-    }
-
-    @Override
-    public ConcreteType<?> getType() {
-        return TYPE;
-    }
-}
diff --git a/src/main/java/org/zwobble/couscous/values/BooleanValue.java b/src/main/java/org/zwobble/couscous/values/BooleanValue.java
new file mode 100644
index 0000000..e05c246
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/BooleanValue.java
@@ -0,0 +1,20 @@
+package org.zwobble.couscous.values;
+
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.Value;
+
+@Value
+public class BooleanValue implements PrimitiveValue {
+    @Getter(value = AccessLevel.NONE)
+    boolean value;
+    
+    public boolean getValue() {
+        return value;
+    }
+
+    @Override
+    public <T> T accept(PrimitiveValueVisitor<T> visitor) {
+        return visitor.visit(this);
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/values/IntegerValue.java b/src/main/java/org/zwobble/couscous/values/IntegerValue.java
new file mode 100644
index 0000000..71c7a41
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/IntegerValue.java
@@ -0,0 +1,17 @@
+package org.zwobble.couscous.values;
+
+import static org.zwobble.couscous.values.TypeReference.typeRef;
+
+import lombok.Value;
+
+@Value
+public class IntegerValue implements PrimitiveValue {
+    public static final TypeReference REF = typeRef("java.lang.Integer");
+    
+    int value;
+
+    @Override
+    public <T> T accept(PrimitiveValueVisitor<T> visitor) {
+        return visitor.visit(this);
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/values/PrimitiveValue.java b/src/main/java/org/zwobble/couscous/values/PrimitiveValue.java
new file mode 100644
index 0000000..2cfe40a
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/PrimitiveValue.java
@@ -0,0 +1,5 @@
+package org.zwobble.couscous.values;
+
+public interface PrimitiveValue {
+    <T> T accept(PrimitiveValueVisitor<T> visitor);
+}
diff --git a/src/main/java/org/zwobble/couscous/values/PrimitiveValueVisitor.java b/src/main/java/org/zwobble/couscous/values/PrimitiveValueVisitor.java
new file mode 100644
index 0000000..07047b8
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/PrimitiveValueVisitor.java
@@ -0,0 +1,8 @@
+package org.zwobble.couscous.values;
+
+public interface PrimitiveValueVisitor<T> {
+    T visit(IntegerValue value);
+    T visit(StringValue value);
+    T visit(BooleanValue value);
+    T visit(UnitValue unitValue);
+}
diff --git a/src/main/java/org/zwobble/couscous/values/PrimitiveValues.java b/src/main/java/org/zwobble/couscous/values/PrimitiveValues.java
new file mode 100644
index 0000000..f6420f0
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/PrimitiveValues.java
@@ -0,0 +1,17 @@
+package org.zwobble.couscous.values;
+
+public class PrimitiveValues {
+    public static final PrimitiveValue UNIT = UnitValue.UNIT;
+    
+    public static PrimitiveValue value(String value) {
+        return new StringValue(value);
+    }
+    
+    public static PrimitiveValue value(int value) {
+        return new IntegerValue(value);
+    }
+    
+    public static PrimitiveValue value(boolean value) {
+        return new BooleanValue(value);
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/values/StringValue.java b/src/main/java/org/zwobble/couscous/values/StringValue.java
new file mode 100644
index 0000000..256d6d1
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/StringValue.java
@@ -0,0 +1,17 @@
+package org.zwobble.couscous.values;
+
+import static org.zwobble.couscous.values.TypeReference.typeRef;
+
+import lombok.Value;
+
+@Value
+public class StringValue implements PrimitiveValue {
+    public static final TypeReference REF = typeRef("java.lang.String");
+
+    String value;
+
+    @Override
+    public <T> T accept(PrimitiveValueVisitor<T> visitor) {
+        return visitor.visit(this);
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/values/UnitValue.java b/src/main/java/org/zwobble/couscous/values/UnitValue.java
new file mode 100644
index 0000000..14bf327
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/UnitValue.java
@@ -0,0 +1,13 @@
+package org.zwobble.couscous.values;
+
+public class UnitValue implements PrimitiveValue {
+    static final UnitValue UNIT = new UnitValue();
+    
+    private UnitValue() {
+    }
+    
+    @Override
+    public <T> T accept(PrimitiveValueVisitor<T> visitor) {
+        return visitor.visit(this);
+    }
+}