First cut.

quephird · Mar 22, 2024 · 3cd6662 · 3cd6662
1 parent 7c68a60
commit 3cd6662
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Showing 2 changed files with 16 additions and 4 deletions.
diff --git a/slox/Interpreter.swift b/slox/Interpreter.swift
@@ -384,13 +384,25 @@ class Interpreter {
             return .string(leftString + rightString)
         }
 
+        if case .instance(let leftList as LoxList) = leftValue,
+           case .instance(let rightList as LoxList) = rightValue,
+           case .plus = oper.type {
+            guard case .instance(let listClass as LoxClass) = try environment.getValue(name: "List") else {
+                fatalError()
+            }
+
+            let newElements = leftList.elements + rightList.elements
+            let list = LoxList(elements: newElements, klass: listClass)
+            return .instance(list)
+        }
+
         switch oper.type {
         case .bangEqual:
             return .boolean(!leftValue.isEqual(to: rightValue))
         case .equalEqual:
             return .boolean(leftValue.isEqual(to: rightValue))
         case .plus:
-            throw RuntimeError.binaryOperandsMustBeNumbersOrStrings
+            throw RuntimeError.binaryOperandsMustBeNumbersOrStringsOrLists
         case .minus, .star, .slash, .greater, .greaterEqual, .less, .lessEqual:
             throw RuntimeError.binaryOperandsMustBeNumbers
         default:

diff --git a/slox/RuntimeError.swift b/slox/RuntimeError.swift
@@ -11,7 +11,7 @@ enum RuntimeError: CustomStringConvertible, Equatable, LocalizedError {
     case unaryOperandMustBeNumber
     case unsupportedUnaryOperator
     case binaryOperandsMustBeNumbers
-    case binaryOperandsMustBeNumbersOrStrings
+    case binaryOperandsMustBeNumbersOrStringsOrLists
     case unsupportedBinaryOperator
     case undefinedVariable(String)
     case notAFunctionDeclaration
@@ -34,8 +34,8 @@ enum RuntimeError: CustomStringConvertible, Equatable, LocalizedError {
             return "Error: unsupported unary operator"
         case .binaryOperandsMustBeNumbers:
             return "Error: operands must be both numbers"
-        case .binaryOperandsMustBeNumbersOrStrings:
-            return "Error: operands must be either both numbers or both strings"
+        case .binaryOperandsMustBeNumbersOrStringsOrLists:
+            return "Error: operands must be either both numbers, strings, or lists"
         case .unsupportedBinaryOperator:
             return "Error: unsupported binary operator"
         case .undefinedVariable(let name):