hash

code/code.go

@@ -30,6 +30,7 @@ const (
 	OpGetGlobal
 	OpSetGlobal
 	OpArray
+	OpHash
 )
 
 type Definition struct {
@@ -57,6 +58,7 @@ var definitions = map[Opcode]*Definition{
 	OpGetGlobal:     {"OpGetGlobal", []int{2}},
 	OpSetGlobal:     {"OpSetGlobal", []int{2}},
 	OpArray:         {"OpArray", []int{2}},
+	OpHash:          {"OpHash", []int{2}},
 }
 
 func Lookup(op byte) (*Definition, error) {

compiler/compiler.go

@@ -5,6 +5,7 @@ import (
 	"monkey/ast"
 	"monkey/code"
 	"monkey/object"
+	"sort"
 )
 
 type EmittedInstruction struct {
@@ -204,6 +205,28 @@ func (c *Compiler) Compile(node ast.Node) error {
 
 		c.emit(code.OpArray, len(node.Elements))
 
+	case *ast.HashLiteral:
+		keys := []ast.Expression{}
+		for k := range node.Pairs {
+			keys = append(keys, k)
+		}
+		sort.Slice(keys, func(i, j int) bool {
+			return keys[i].String() < keys[j].String()
+		})
+
+		for _, k := range keys {
+			err := c.Compile(k)
+			if err != nil {
+				return err
+			}
+			err = c.Compile(node.Pairs[k])
+			if err != nil {
+				return err
+			}
+		}
+
+		c.emit(code.OpHash, len(node.Pairs)*2)
+
 	}
 
 	return nil

compiler/compiler_test.go

@@ -345,6 +345,51 @@ func TestArrayLiterals(t *testing.T) {
 	runCompilerTests(t, tests)
 }
 
+func TestHashLiterals(t *testing.T) {
+	tests := []compilerTestCase{
+		{
+			input:             "{}",
+			expectedConstants: []interface{}{},
+			expectedInstructions: []code.Instructions{
+				code.Make(code.OpHash, 0),
+				code.Make(code.OpPop),
+			},
+		},
+		{
+			input:             "{1: 2, 3: 4, 5: 6}",
+			expectedConstants: []interface{}{1, 2, 3, 4, 5, 6},
+			expectedInstructions: []code.Instructions{
+				code.Make(code.OpConstant, 0),
+				code.Make(code.OpConstant, 1),
+				code.Make(code.OpConstant, 2),
+				code.Make(code.OpConstant, 3),
+				code.Make(code.OpConstant, 4),
+				code.Make(code.OpConstant, 5),
+				code.Make(code.OpHash, 6),
+				code.Make(code.OpPop),
+			},
+		},
+		{
+			input:             "{1: 2 + 3, 4: 5 * 6}",
+			expectedConstants: []interface{}{1, 2, 3, 4, 5, 6},
+			expectedInstructions: []code.Instructions{
+				code.Make(code.OpConstant, 0),
+				code.Make(code.OpConstant, 1),
+				code.Make(code.OpConstant, 2),
+				code.Make(code.OpAdd),
+				code.Make(code.OpConstant, 3),
+				code.Make(code.OpConstant, 4),
+				code.Make(code.OpConstant, 5),
+				code.Make(code.OpMul),
+				code.Make(code.OpHash, 4),
+				code.Make(code.OpPop),
+			},
+		},
+	}
+
+	runCompilerTests(t, tests)
+}
+
 func runCompilerTests(t *testing.T, tests []compilerTestCase) {
 	t.Helper()
 

vm/vm.go

@@ -145,12 +145,47 @@ func (vm *VM) Run() error {
 				return err
 			}
 
+		case code.OpHash:
+			numElements := int(code.ReadUint16(vm.instructions[ip+1:]))
+			ip += 2
+
+			hash, err := vm.buildHash(vm.sp-numElements, vm.sp)
+			if err != nil {
+				return err
+			}
+			vm.sp = vm.sp - numElements
+
+			err = vm.push(hash)
+			if err != nil {
+				return err
+			}
+
 		}
 	}
 
 	return nil
 }
 
+func (vm *VM) buildHash(startIndex, endIndex int) (object.Object, error) {
+	hashedPairs := make(map[object.HashKey]object.HashPair)
+
+	for i := startIndex; i < endIndex; i += 2 {
+		key := vm.stack[i]
+		value := vm.stack[i+1]
+
+		pair := object.HashPair{Key: key, Value: value}
+
+		hashKey, ok := key.(object.Hashable)
+		if !ok {
+			return nil, fmt.Errorf("unusable as hash key: %s", key.Type())
+		}
+
+		hashedPairs[hashKey.HashKey()] = pair
+	}
+
+	return &object.Hash{Pairs: hashedPairs}, nil
+}
+
 func (vm *VM) buildArray(startIndex, endIndex int) object.Object {
 	elements := make([]object.Object, endIndex-startIndex)
 

vm/vm_test.go

@@ -79,6 +79,29 @@ func testExpectedObject(t *testing.T, expected interface{}, actual object.Object
 			}
 		}
 
+	case map[object.HashKey]int64:
+		hash, ok := actual.(*object.Hash)
+		if !ok {
+			t.Errorf("object not Hash: %T (%+v)", actual, actual)
+		}
+
+		if len(hash.Pairs) != len(expected) {
+			t.Errorf("wrong num of Pairs. want=%d, got=%d", len(expected), len(hash.Pairs))
+			return
+		}
+
+		for expectedKey, expectedValue := range expected {
+			pair, ok := hash.Pairs[expectedKey]
+			if !ok {
+				t.Errorf("no pair for given key in Pairs")
+			}
+
+			err := testIntegerObject(expectedValue, pair.Value)
+			if err != nil {
+				t.Errorf("testIntgerObject failed: %s", err)
+			}
+		}
+
 	case *object.Null:
 		if actual != Null {
 			t.Errorf("object is not Null: %T (%+v)", actual, actual)
@@ -232,3 +255,27 @@ func TestArrayLiterals(t *testing.T) {
 
 	runVmTests(t, tests)
 }
+
+func TestHashLiterals(t *testing.T) {
+	tests := []vmTestCase{
+		{
+			"{}", map[object.HashKey]int64{},
+		},
+		{
+			"{1: 2, 2: 3}",
+			map[object.HashKey]int64{
+				(&object.Integer{Value: 1}).HashKey(): 2,
+				(&object.Integer{Value: 2}).HashKey(): 3,
+			},
+		},
+		{
+			"{1 + 1: 2 * 2, 3 + 3: 4 * 4}",
+			map[object.HashKey]int64{
+				(&object.Integer{Value: 2}).HashKey(): 4,
+				(&object.Integer{Value: 6}).HashKey(): 16,
+			},
+		},
+	}
+
+	runVmTests(t, tests)
+}