From 290d8d0f0af985767f197b6cef1157409de1adab Mon Sep 17 00:00:00 2001
From: Alex Zenla <alex@fork.run>
Date: Tue, 5 Sep 2023 03:13:43 -0700
Subject: [PATCH] evaluator: optimize the cost of defining a variable in a
 scope

---
 .../pizza/pork/evaluator/FastVariableCache.kt  | 18 ------------------
 .../kotlin/gay/pizza/pork/evaluator/Scope.kt   |  5 +++--
 2 files changed, 3 insertions(+), 20 deletions(-)
 delete mode 100644 evaluator/src/main/kotlin/gay/pizza/pork/evaluator/FastVariableCache.kt

diff --git a/evaluator/src/main/kotlin/gay/pizza/pork/evaluator/FastVariableCache.kt b/evaluator/src/main/kotlin/gay/pizza/pork/evaluator/FastVariableCache.kt
deleted file mode 100644
index 96c7bbf..0000000
--- a/evaluator/src/main/kotlin/gay/pizza/pork/evaluator/FastVariableCache.kt
+++ /dev/null
@@ -1,18 +0,0 @@
-package gay.pizza.pork.evaluator
-
-class FastVariableCache {
-  private val cache = mutableMapOf<String, Any>()
-
-  fun put(key: String, value: Any) {
-    cache[key] = value
-  }
-
-  fun lookup(key: String): Any = cache[key] ?: NotFound
-  fun has(key: String): Boolean = cache.containsKey(key)
-
-  fun invalidate(key: String) {
-    cache.remove(key)
-  }
-
-  object NotFound
-}
diff --git a/evaluator/src/main/kotlin/gay/pizza/pork/evaluator/Scope.kt b/evaluator/src/main/kotlin/gay/pizza/pork/evaluator/Scope.kt
index 296bfff..25df9bd 100644
--- a/evaluator/src/main/kotlin/gay/pizza/pork/evaluator/Scope.kt
+++ b/evaluator/src/main/kotlin/gay/pizza/pork/evaluator/Scope.kt
@@ -5,10 +5,11 @@ class Scope(val parent: Scope? = null, inherits: List<Scope> = emptyList()) {
   private val variables = mutableMapOf<String, Any>()
 
   fun define(name: String, value: Any) {
-    if (variables.containsKey(name)) {
+    val previous = variables.put(name, value)
+    if (previous != null) {
+      variables[name] = previous
       throw RuntimeException("Variable '${name}' is already defined")
     }
-    variables[name] = value
   }
 
   fun value(name: String): Any {