From e29b85d0d760e09b3a653bba55285d049cfc4673 Mon Sep 17 00:00:00 2001
From: BlockChainDev <kevtheappdev@gmail.com>
Date: Wed, 27 Feb 2019 20:50:00 +0000
Subject: [PATCH] VM:Add abstract stack item

---
 pkg/vm/stack/stackitem.go | 42 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 pkg/vm/stack/stackitem.go

diff --git a/pkg/vm/stack/stackitem.go b/pkg/vm/stack/stackitem.go
new file mode 100644
index 000000000..9f29f9d3b
--- /dev/null
+++ b/pkg/vm/stack/stackitem.go
@@ -0,0 +1,42 @@
+package stack
+
+import (
+	"errors"
+)
+
+//Item is an interface which represents object that can be placed on the stack
+type Item interface {
+	Integer() (*Int, error)
+	Boolean() (*Boolean, error)
+	ByteArray() (*ByteArray, error)
+	Array() (*Array, error)
+}
+
+// Represents an `abstract` stack item
+// which will hold default values for stack items
+// this is intended to be embedded into types that you will use on the stack
+type abstractItem struct{}
+
+// Integer is the default implementation for a stackItem
+// Implements Item interface
+func (a *abstractItem) Integer() (*Int, error) {
+	return nil, errors.New("This stack item is not an Integer")
+}
+
+// Boolean is the default implementation for a stackItem
+// Implements Item interface
+func (a *abstractItem) Boolean() (*Boolean, error) {
+	return nil, errors.New("This stack item is not a Boolean")
+}
+
+// ByteArray is the default implementation for a stackItem
+// Implements Item interface
+func (a *abstractItem) ByteArray() (*ByteArray, error) {
+	return nil, errors.New("This stack item is not a byte array")
+}
+
+// Array is the default implementation for a stackItem
+// Implements Item interface
+func (a *abstractItem) Array() (*Array, error) {
+	return nil, errors.New("This stack item is not an array")
+}