Refactor VM and operators

internal/object/array.go

@@ -2,6 +2,7 @@ package object
 
 import (
 	"bytes"
+	"fmt"
 	"strings"
 )
 
@@ -18,30 +19,30 @@ func (ao *Array) Bool() bool {
 	return len(ao.Elements) > 0
 }
 
-func (a *Array) PopLeft() Object {
-	if len(a.Elements) > 0 {
-		e := a.Elements[0]
-		a.Elements = a.Elements[1:]
+func (ao *Array) PopLeft() Object {
+	if len(ao.Elements) > 0 {
+		e := ao.Elements[0]
+		ao.Elements = ao.Elements[1:]
 		return e
 	}
 	return &Null{}
 }
 
-func (a *Array) PopRight() Object {
-	if len(a.Elements) > 0 {
-		e := a.Elements[(len(a.Elements) - 1)]
-		a.Elements = a.Elements[:(len(a.Elements) - 1)]
+func (ao *Array) PopRight() Object {
+	if len(ao.Elements) > 0 {
+		e := ao.Elements[(len(ao.Elements) - 1)]
+		ao.Elements = ao.Elements[:(len(ao.Elements) - 1)]
 		return e
 	}
 	return &Null{}
 }
 
-func (a *Array) Prepend(obj Object) {
-	a.Elements = append([]Object{obj}, a.Elements...)
+func (ao *Array) Prepend(obj Object) {
+	ao.Elements = append([]Object{obj}, ao.Elements...)
 }
 
-func (a *Array) Append(obj Object) {
-	a.Elements = append(a.Elements, obj)
+func (ao *Array) Append(obj Object) {
+	ao.Elements = append(ao.Elements, obj)
 }
 
 func (ao *Array) Inspect() string {
@@ -69,6 +70,63 @@ func (ao *Array) Less(i, j int) bool {
 	return false
 }
 
+func (ao *Array) Add(other Object) (Object, error) {
+	if other.Type() != ao.Type() {
+		return nil, NewBinaryOpError(ao, other, "+")
+	}
+
+	var elements []Object
+	elements = append(elements, ao.Elements...)
+	elements = append(elements, other.(*Array).Elements...)
+
+	return &Array{Elements: elements}, nil
+
+}
+
+func (ao *Array) Mul(other Object) (Object, error) {
+	if other.Type() != IntegerType {
+		return nil, NewBinaryOpError(ao, other, "*")
+	}
+
+	var elements []Object
+	N := int(other.(*Integer).Value)
+	for i := 0; i < N; i++ {
+		elements = append(elements, ao.Elements...)
+	}
+
+	return &Array{Elements: elements}, nil
+}
+
+func (ao *Array) Get(index Object) (Object, error) {
+	if !AssertTypes(index, IntegerType) {
+		return nil, fmt.Errorf("invalid type for array index, expected Integer got %s", index.Type())
+	}
+
+	i := index.(*Integer).Value
+	N := int64(len(ao.Elements))
+	if i < 0 || i >= N {
+		return &Null{}, nil
+	}
+
+	return ao.Elements[i], nil
+}
+
+func (ao *Array) Set(index, other Object) error {
+	if !AssertTypes(index, IntegerType) {
+		return fmt.Errorf("invalid type for array index, expected Integer got %s", index.Type())
+	}
+
+	i := index.(*Integer).Value
+	N := int64(len(ao.Elements))
+	if i < 0 || i >= N {
+		return fmt.Errorf("index out of bounds %d with array length %d", i, N)
+	}
+
+	ao.Elements[i] = other
+
+	return nil
+}
+
 func (ao *Array) Compare(other Object) int {
 	if obj, ok := other.(*Array); ok {
 		if len(ao.Elements) != len(obj.Elements) {

internal/object/bool.go

@@ -35,6 +35,24 @@ func (b *Boolean) Int() int {
 	return 0
 }
 
+func (b *Boolean) LogicalAnd(other Object) (Object, error) {
+	if !AssertTypes(other, BooleanType, IntegerType) {
+		return nil, NewBinaryOpError(b, other, "&&")
+	}
+	return &Boolean{b.Value && other.Bool()}, nil
+}
+
+func (b *Boolean) LogicalOr(other Object) (Object, error) {
+	if !AssertTypes(other, BooleanType, IntegerType) {
+		return nil, NewBinaryOpError(b, other, "||")
+	}
+	return &Boolean{b.Value || other.Bool()}, nil
+}
+
+func (b *Boolean) LogicalNot() Object {
+	return &Boolean{!b.Value}
+}
+
 func (b *Boolean) Compare(other Object) int {
 	if obj, ok := other.(*Boolean); ok {
 		return b.Int() - obj.Int()

internal/object/error.go

@@ -1,5 +1,7 @@
 package object
 
+// error encountered. This object is tracked through the evaluator and when
+// encountered stops evaluation of the program or body of a function.
 type Error struct {
 	Message string
 }

internal/object/errors.go

@@ -0,0 +1,20 @@
+package object
+
+import (
+	"fmt"
+)
+
+// BinaryOpError is an binary operation error usually resulting from mismatched types
+type BinaryOpError struct {
+	left, right Object
+	op          string
+}
+
+func (e BinaryOpError) Error() string {
+	return fmt.Sprintf("unsupported types for binary operation: %s %s %s", e.left.Type(), e.op, e.right.Type())
+}
+
+// NewBinaryOpError returns a new BinaryOpError
+func NewBinaryOpError(left, right Object, op string) BinaryOpError {
+	return BinaryOpError{left, right, op}
+}

internal/object/hash.go

@@ -75,6 +75,46 @@ func (h *Hash) String() string {
 	return h.Inspect()
 }
 
+func (h *Hash) Add(other Object) (Object, error) {
+	if other.Type() != h.Type() {
+		return nil, NewBinaryOpError(h, other, "+")
+	}
+
+	pairs := make(map[HashKey]HashPair)
+	for k, v := range h.Pairs {
+		pairs[k] = v
+	}
+	for k, v := range other.(*Hash).Pairs {
+		pairs[k] = v
+	}
+	return &Hash{Pairs: pairs}, nil
+}
+
+func (h *Hash) Get(index Object) (Object, error) {
+	key, ok := index.(Hashable)
+	if !ok {
+		return nil, fmt.Errorf("invalid hash key %s", index.Type())
+	}
+
+	pair, found := h.Pairs[key.HashKey()]
+	if !found {
+		return &Null{}, nil
+	}
+
+	return pair.Value, nil
+}
+
+func (h *Hash) Set(index, other Object) error {
+	key, ok := index.(Hashable)
+	if !ok {
+		return fmt.Errorf("invalid hash key %s", index.Type())
+	}
+
+	h.Pairs[key.HashKey()] = HashPair{Key: index, Value: other}
+
+	return nil
+}
+
 func (h *Hash) Compare(other Object) int {
 	if obj, ok := other.(*Hash); ok {
 		if len(h.Pairs) != len(obj.Pairs) {

internal/object/int.go

@@ -26,6 +26,94 @@ func (i *Integer) String() string {
 	return i.Inspect()
 }
 
+func (i *Integer) Add(other Object) (Object, error) {
+	if !AssertTypes(other, IntegerType) {
+		return nil, NewBinaryOpError(i, other, "+")
+	}
+	return &Integer{i.Value + other.(*Integer).Value}, nil
+}
+
+func (i *Integer) Sub(other Object) (Object, error) {
+	if !AssertTypes(other, IntegerType) {
+		return nil, NewBinaryOpError(i, other, "-")
+	}
+	return &Integer{i.Value - other.(*Integer).Value}, nil
+}
+
+func (i *Integer) Mul(other Object) (Object, error) {
+	switch other.Type() {
+	case IntegerType:
+		return &Integer{i.Value * other.(*Integer).Value}, nil
+	case StringType:
+		return other.(Mul).Mul(i)
+	case ArrayType:
+		return other.(Mul).Mul(i)
+	default:
+		return nil, NewBinaryOpError(i, other, "*")
+	}
+}
+
+func (i *Integer) Div(other Object) (Object, error) {
+	if !AssertTypes(other, IntegerType) {
+		return nil, NewBinaryOpError(i, other, "/")
+	}
+	return &Integer{i.Value / other.(*Integer).Value}, nil
+}
+
+func (i *Integer) Mod(other Object) (Object, error) {
+	if !AssertTypes(other, IntegerType) {
+		return nil, NewBinaryOpError(i, other, "%")
+	}
+	return &Integer{i.Value % other.(*Integer).Value}, nil
+}
+
+func (i *Integer) BitwiseOr(other Object) (Object, error) {
+	if !AssertTypes(other, IntegerType) {
+		return nil, NewBinaryOpError(i, other, "|")
+	}
+	return &Integer{i.Value | other.(*Integer).Value}, nil
+}
+
+func (i *Integer) BitwiseXor(other Object) (Object, error) {
+	if !AssertTypes(other, IntegerType) {
+		return nil, NewBinaryOpError(i, other, "^")
+	}
+	return &Integer{i.Value ^ other.(*Integer).Value}, nil
+}
+
+func (i *Integer) BitwiseAnd(other Object) (Object, error) {
+	if !AssertTypes(other, IntegerType) {
+		return nil, NewBinaryOpError(i, other, "&")
+	}
+	return &Integer{i.Value & other.(*Integer).Value}, nil
+}
+
+func (i *Integer) BitwiseNot() Object {
+	return &Integer{^i.Value}
+}
+
+func (i *Integer) LeftShift(other Object) (Object, error) {
+	if !AssertTypes(other, IntegerType) {
+		return nil, NewBinaryOpError(i, other, "<<")
+	}
+	return &Integer{i.Value << other.(*Integer).Value}, nil
+}
+
+func (i *Integer) RightShift(other Object) (Object, error) {
+	if !AssertTypes(other, IntegerType) {
+		return nil, NewBinaryOpError(i, other, ">>")
+	}
+	return &Integer{i.Value >> other.(*Integer).Value}, nil
+}
+
+func (i *Integer) LogicalNot() Object {
+	return &Boolean{!i.Bool()}
+}
+
+func (i *Integer) Negate() Object {
+	return &Integer{-i.Value}
+}
+
 func (i *Integer) Compare(other Object) int {
 	if obj, ok := other.(*Integer); ok {
 		switch {

internal/object/module.go

@@ -24,6 +24,20 @@ func (m Module) Inspect() string {
 	return fmt.Sprintf("<module '%s'>", m.Name)
 }
 
+func (m *Module) Get(index Object) (Object, error) {
+	key, ok := index.(Hashable)
+	if !ok {
+		return nil, fmt.Errorf("invalid module attribute %s", index.Type())
+	}
+
+	attr, found := m.Attrs.(*Hash).Pairs[key.HashKey()]
+	if !found {
+		return &Null{}, nil
+	}
+
+	return attr.Value, nil
+}
+
 func (m Module) Compare(other Object) int {
 	return 1
 }

internal/object/null.go

@@ -18,6 +18,10 @@ func (n *Null) String() string {
 	return n.Inspect()
 }
 
+func (n *Null) LogicalNot() Object {
+	return &Boolean{!n.Bool()}
+}
+
 func (n *Null) Compare(other Object) int {
 	if _, ok := other.(*Null); ok {
 		return 0

internal/object/object.go

@@ -54,6 +54,91 @@ func (t Type) String() string {
 	}
 }
 
+// Add is the interface for binary addition
+type Add interface {
+	Add(other Object) (Object, error)
+}
+
+// Sub is the interface for binary subtraction
+type Sub interface {
+	Sub(other Object) (Object, error)
+}
+
+// Mul is the interface for binary multiplication
+type Mul interface {
+	Mul(other Object) (Object, error)
+}
+
+// Div is the interface for binary division
+type Div interface {
+	Div(other Object) (Object, error)
+}
+
+// Mod is the interface for binary modulo
+type Mod interface {
+	Mod(other Object) (Object, error)
+}
+
+// LogicalOr is the interface for logical or
+type LogicalOr interface {
+	LogicalOr(other Object) (Object, error)
+}
+
+// LogicalAnd is the interface for logical and
+type LogicalAnd interface {
+	LogicalAnd(other Object) (Object, error)
+}
+
+// BitwiseOr is the interface for bitwise or
+type BitwiseOr interface {
+	BitwiseOr(other Object) (Object, error)
+}
+
+// BitwiseAnd is the interface for bitwise and
+type BitwiseAnd interface {
+	BitwiseAnd(other Object) (Object, error)
+}
+
+// BitwiseXor is the interface for bitwise xor
+type BitwiseXor interface {
+	BitwiseXor(other Object) (Object, error)
+}
+
+// BitwiseNot is the interface for bitwise not
+type BitwiseNot interface {
+	BitwiseNot() Object
+}
+
+// LeftShift is the interface for bitwise left shift
+type LeftShift interface {
+	LeftShift(other Object) (Object, error)
+}
+
+// RightShift is the interface for bitwise right shift
+type RightShift interface {
+	RightShift(other Object) (Object, error)
+}
+
+// LogicalNot is the interface for logical not
+type LogicalNot interface {
+	LogicalNot() Object
+}
+
+// Negate is the interface for unary negation
+type Negate interface {
+	Negate() Object
+}
+
+// Setter is the interface for assigning a value to an index
+type Setter interface {
+	Set(index, value Object) error
+}
+
+// Getter is the interface for getting a value from an index
+type Getter interface {
+	Get(index Object) (Object, error)
+}
+
 // Comparable is the interface for comparing two Object and their underlying
 // values. It is the responsibility of the caller (left) to check for types.
 // Returns `true` iif the types and values are identical, `false` otherwise.
@@ -91,3 +176,12 @@ type Hashable interface {
 
 // BuiltinFunction represents the builtin function type
 type BuiltinFunction func(args ...Object) Object
+
+func AssertTypes(obj Object, types ...Type) bool {
+	for _, t := range types {
+		if t == obj.Type() {
+			return true
+		}
+	}
+	return false
+}

internal/object/str.go

@@ -2,6 +2,7 @@ package object
 
 import (
 	"fmt"
+	"strings"
 	"unicode/utf8"
 )
 
@@ -33,6 +34,33 @@ func (s *String) String() string {
 	return s.Value
 }
 
+func (s *String) Add(other Object) (Object, error) {
+	if !AssertTypes(other, StringType) {
+		return nil, NewBinaryOpError(s, other, "+")
+	}
+	return &String{s.Value + other.(*String).Value}, nil
+}
+
+func (s *String) Mul(other Object) (Object, error) {
+	if !AssertTypes(other, IntegerType) {
+		return nil, NewBinaryOpError(s, other, "*")
+	}
+	return &String{strings.Repeat(s.Value, int(other.(*Integer).Value))}, nil
+}
+
+func (s *String) Get(index Object) (Object, error) {
+	if !AssertTypes(index, IntegerType) {
+		return nil, fmt.Errorf("invalid type for string index, expected Integer got %s", index.Type())
+	}
+
+	i := int(index.(*Integer).Value)
+	if i < 0 || i >= len(s.Value) {
+		return &String{}, nil
+	}
+
+	return &String{string(s.Value[i])}, nil
+}
+
 func (s *String) Compare(other Object) int {
 	if obj, ok := other.(*String); ok {
 		switch {