diff --git a/src/main/kotlin/lumen/runtime/Value.kt b/src/main/kotlin/lumen/runtime/Value.kt
new file mode 100644
index 0000000..c65d34b
--- /dev/null
+++ b/src/main/kotlin/lumen/runtime/Value.kt
@@ -0,0 +1,115 @@
+package lumen.runtime
+
+import lumen.bytecode.Chunk
+
+sealed class Value
+
+object NilValue : Value()
+
+data class IntValue(val value: Long) : Value()
+
+data class DoubleValue(val value: Double) : Value()
+
+data class BoolValue(val value: Boolean) : Value()
+
+data class StringValue(val value: String) : Value()
+
+class ListValue(val items: MutableList<Value> = mutableListOf()) : Value()
+
+class MapValue(val entries: LinkedHashMap<Value, Value> = LinkedHashMap()) : Value()
+
+class RangeValue(val start: Long, val end: Long, val step: Long) : Value() {
+    fun length(): Long {
+        if (step > 0) {
+            if (end <= start) return 0
+            return (end - start + step - 1) / step
+        }
+        if (start <= end) return 0
+        return (start - end + (-step) - 1) / (-step)
+    }
+
+    fun elementAt(index: Long): Long = start + index * step
+}
+
+class FunctionValue(
+    val name: String,
+    val arity: Int,
+    val chunk: Chunk,
+    val upvalueCount: Int
+) : Value()
+
+class Upvalue(var location: Int) : Value() {
+    var closed: Value = NilValue
+    val isClosed: Boolean get() = location < 0
+}
+
+class ClosureValue(val function: FunctionValue, val upvalues: Array<Upvalue>) : Value()
+
+class NativeFunctionValue(
+    val name: String,
+    val arity: IntRange,
+    val call: (List<Value>) -> Value
+) : Value()
+
+class IteratorValue(val iterator: Iterator<Value>) : Value()
+
+fun isTruthy(value: Value): Boolean = when (value) {
+    is NilValue -> false
+    is BoolValue -> value.value
+    else -> true
+}
+
+fun valuesEqual(a: Value, b: Value): Boolean = when {
+    a is IntValue && b is IntValue -> a.value == b.value
+    a is DoubleValue && b is DoubleValue -> a.value == b.value
+    a is IntValue && b is DoubleValue -> a.value.toDouble() == b.value
+    a is DoubleValue && b is IntValue -> a.value == b.value.toDouble()
+    a is StringValue && b is StringValue -> a.value == b.value
+    a is BoolValue && b is BoolValue -> a.value == b.value
+    a is NilValue && b is NilValue -> true
+    else -> a === b
+}
+
+fun typeName(value: Value): String = when (value) {
+    is NilValue -> "nil"
+    is IntValue -> "int"
+    is DoubleValue -> "double"
+    is BoolValue -> "bool"
+    is StringValue -> "string"
+    is ListValue -> "list"
+    is MapValue -> "map"
+    is RangeValue -> "range"
+    is FunctionValue -> "function"
+    is ClosureValue -> "function"
+    is NativeFunctionValue -> "function"
+    is Upvalue -> "upvalue"
+    is IteratorValue -> "iterator"
+}
+
+fun displayString(value: Value): String = when (value) {
+    is NilValue -> "nil"
+    is IntValue -> value.value.toString()
+    is DoubleValue -> formatDouble(value.value)
+    is BoolValue -> value.value.toString()
+    is StringValue -> value.value
+    is ListValue -> value.items.joinToString(prefix = "[", postfix = "]") { reprString(it) }
+    is MapValue -> value.entries.entries.joinToString(prefix = "{", postfix = "}") {
+        "${reprString(it.key)}: ${reprString(it.value)}"
+    }
+    is RangeValue -> "range(${value.start}, ${value.end}, ${value.step})"
+    is FunctionValue -> "<fn ${value.name}>"
+    is ClosureValue -> "<fn ${value.function.name}>"
+    is NativeFunctionValue -> "<native ${value.name}>"
+    is Upvalue -> "<upvalue>"
+    is IteratorValue -> "<iterator>"
+}
+
+private fun reprString(value: Value): String =
+    if (value is StringValue) "\"${value.value}\"" else displayString(value)
+
+private fun formatDouble(d: Double): String {
+    if (d.isNaN()) return "nan"
+    if (d.isInfinite()) return if (d > 0) "inf" else "-inf"
+    if (d == d.toLong().toDouble()) return "${d.toLong()}.0"
+    return d.toString()
+}