Hashes

object/object.go

@@ -3,6 +3,7 @@ package object
 import (
 	"bytes"
 	"fmt"
+	"hash/fnv"
 	"monkey/ast"
 	"strings"
 )
@@ -19,6 +20,7 @@ const (
 	STRING_OBJ       = "STRING"
 	BUILTIN_OBJ      = "BUILTIN"
 	ARRAY_OBJ        = "ARRAY"
+	HASH_OBJ         = "HASH"
 )
 
 type Object interface {
@@ -157,3 +159,63 @@ func (ao Array) Inspect() string {
 
 	return out.String()
 }
+
+type HashKey struct {
+	Type  ObjectType
+	Value uint64
+}
+
+func (b *Boolean) HashKey() HashKey {
+	var value uint64
+
+	if b.Value {
+		value = 1
+	} else {
+		value = 0
+	}
+
+	return HashKey{Type: b.Type(), Value: value}
+}
+
+type Hashable interface {
+	HashKey() HashKey
+}
+
+func (i *Integer) HashKey() HashKey {
+	return HashKey{Type: i.Type(), Value: uint64(i.Value)}
+}
+
+func (s *String) HashKey() HashKey {
+	h := fnv.New64a()
+	h.Write([]byte(s.Value))
+
+	return HashKey{Type: s.Type(), Value: h.Sum64()}
+}
+
+type HashPair struct {
+	Key   Object
+	Value Object
+}
+
+type Hash struct {
+	Pairs map[HashKey]HashPair
+}
+
+func (h *Hash) Type() ObjectType {
+	return HASH_OBJ
+}
+
+func (h *Hash) Inspect() string {
+	var out bytes.Buffer
+
+	pairs := []string{}
+	for _, pair := range h.Pairs {
+		pairs = append(pairs, fmt.Sprintf("%s: %s", pair.Key.Inspect(), pair.Value.Inspect()))
+	}
+
+	out.WriteString("{")
+	out.WriteString(strings.Join(pairs, ", "))
+	out.WriteString("}")
+
+	return out.String()
+}

object/object_test.go

@@ -0,0 +1,22 @@
+package object
+
+import "testing"
+
+func TestStringHashKey(t *testing.T) {
+	hello1 := &String{Value: "Hello World"}
+	hello2 := &String{Value: "Hello World"}
+	diff1 := &String{Value: "My name is johnny"}
+	diff2 := &String{Value: "My name is johnny"}
+
+	if hello1.HashKey() != hello2.HashKey() {
+		t.Errorf("string with same content have different hash keys")
+	}
+
+	if diff1.HashKey() != diff2.HashKey() {
+		t.Errorf("string with same content have different hash keys")
+	}
+
+	if hello1.HashKey() == diff1.HashKey() {
+		t.Errorf("string with different content have same hash keys")
+	}
+}