Initial data commit

Task/Stack/Go/stack-6.go

@@ -0,0 +1,53 @@
+package main
+
+import "fmt"
+
+type stack []interface{}
+
+func (k *stack) push(s interface{}) {
+    *k = append(*k, s)
+}
+
+func (k *stack) pop() (s interface{}, ok bool) {
+    if k.empty() {
+        return
+    }
+    last := len(*k) - 1
+    s = (*k)[last]
+    *k = (*k)[:last]
+    return s, true
+}
+
+func (k *stack) peek() (s interface{}, ok bool) {
+    if k.empty() {
+        return
+    }
+    last := len(*k) - 1
+    s = (*k)[last]
+    return s, true
+}
+
+func (k *stack) empty() bool {
+    return len(*k) == 0
+}
+
+func main() {
+    var s stack
+    fmt.Println("new stack:", s)
+    fmt.Println("empty?", s.empty())
+    s.push(3)
+    fmt.Println("push 3. stack:", s)
+    fmt.Println("empty?", s.empty())
+    s.push("four")
+    fmt.Println(`push "four" stack:`, s)
+    if top, ok := s.peek(); ok {
+        fmt.Println("top value:", top)
+    } else {
+        fmt.Println("nothing on stack")
+    }
+    if popped, ok := s.pop(); ok {
+        fmt.Println(popped, "popped.  stack:", s)
+    } else {
+        fmt.Println("nothing to pop")
+    }
+}