Adde migration guidelines

Author: christianrpetrin

MIGRATE_V1_TO_V2.md

@@ -0,0 +1,135 @@
+# How to Migrate from Deque V1 to V2
+
+After have downloaded Deque v2 version into your project (`go get -u github.com/ef-ds/deque/v2`), below code changes are required in order to migrate to v2.
+
+- Update the imports path from `github.com/ef-ds/deque` to `deque github.com/ef-ds/deque/v2`
+- Update the Deque's declaration from `var d deque.Deque` to `var d deque.Deque[data_type]` and/or `d := deque.New()` to `d := deque.New[data_type]()`
+- Remove any `interface{}` type casts (i.e. `var v, _ := d.Pop(); typeCast := v.(data_type)`)
+
+Below are examples of migrated code:
+
+Simple int as data type - V1 version:
+```go
+import "github.com/ef-ds/deque"
+
+var d deque.Deque
+for i := 1; i <= 5; i++ {
+    d.PushBack(i)
+}
+
+for d.Len() > 0 {
+    v, _ := d.PopFront()
+    intV := v.(int)
+    fmt.Print(intV)
+}
+```
+
+Simple int as data type - V2 version:
+```go
+import deque "github.com/ef-ds/deque/v2"
+
+var d deque.Deque[int]
+for i := 1; i <= 5; i++ {
+    d.PushBack(i)
+}
+
+for d.Len() > 0 {
+    intV, _ := d.PopFront()
+    fmt.Print(intV)
+}
+```
+
+Custom struct as data type - V1 version:
+```go
+import "github.com/ef-ds/deque"
+
+type myType struct {
+    value int
+}
+
+d := deque.New()
+for i := 1; i <= 5; i++ {
+    d.PushBack(&myType{value: i})
+}
+
+for d.Len() > 0 {
+    v, _ := d.PopFront()
+    myTypeV := v.(*myType)
+    fmt.Print(myTypeV.value)
+}
+```
+
+Custom struct as data type - V2 version:
+```go
+import deque "github.com/ef-ds/deque/v2"
+
+type myType struct {
+    value int
+}
+
+d := deque.New[*myType]()
+for i := 1; i <= 15; i++ {
+    d.PushBack(&myType{value: i})
+}
+
+for d.Len() > 0 {
+    v, _ := d.PopFront()
+    fmt.Print(v.value)
+}
+```
+
+Mixed data types used as data type - V1 version:
+```go
+import "github.com/ef-ds/deque"
+
+d := deque.New()
+for i := 1; i <= 5; i++ {
+    if i%2 == 0 {
+        // Push value as int
+        d.PushBack(i)
+    } else {
+        // Push value as string
+        d.PushBack(strconv.Itoa(i))
+    }
+}
+
+for d.Len() > 0 {
+    v, _ := d.PopFront()
+    switch t := v.(type) {
+    case int:
+        fmt.Printf("Int value: %d", t)
+    case string:
+        fmt.Printf("String value: %s", t)
+    default:
+        fmt.Print("Unrecognized type")
+    }
+}
+```
+
+Mixed data types used as data type - V2 version:
+```go
+import deque "github.com/ef-ds/deque/v2"
+
+d := deque.New[interface{}]()
+for i := 1; i <= 5; i++ {
+    if i%2 == 0 {
+        // Push value as int
+        d.PushBack(i)
+    } else {
+        // Push value as string
+        d.PushBack(strconv.Itoa(i))
+    }
+}
+
+for d.Len() > 0 {
+    v, _ := d.PopFront()
+    switch t := v.(type) {
+    case int:
+        fmt.Printf("Int value: %d", t)
+    case string:
+        fmt.Printf("String value: %s", t)
+    default:
+        fmt.Print("Unrecognized type")
+    }
+}
+```

README.md

@@ -86,6 +86,8 @@ Also refer to the [integration](integration_test.go) and [API](api_test.go) test
 
 Starting with v2.0.0, Deque supports generics. Looking for a previous non-generic stable release? Check out version [1.0.4](https://github.com/ef-ds/deque/releases/tag/v1.0.4).
 
+Looking to migrate from v1 to v2? Check [this](MIGRATE_V1_TO_V2.md) out!
+
 
 ## Tests
 Besides having 100% code coverage, deque has an extensive set of [unit](unit_test.go), [integration](integration_test.go) and [API](api_test.go) tests covering all happy, sad and edge cases.