Minimal Stack&Queue data structure Implementation in D

minimalQueue.d

/*
  Minimal Queue data structure Implementation in D
  
  Copyright (c) 2016 alphaKAI
  This software is released under the MIT License.
*/

import core.memory;

struct Node(T) {
  Node!T* next;
  T       value;
}

struct List(T) {
  Node!T* head = null;
  Node!T* tail = null;

  void push(Node!T* node) {
    if (head is null) {
      head = node;
      tail = node;
    } else {
      auto tp   = head;
      head      = node;
      tp.next   = head;
    }
  }

  Node!T* pop() {
    if (tail is null) {
      return null;
    } else {
      if (tail.next is null) {
        auto tp = tail;
        tail    = null;
        head    = null;
        return tp;
      } else {
        auto tp = tail;
        tail    = tp.next;
        return tp;
      }
    }
  }

  @property bool empty() {
    return tail is null;
  }
}

struct Queue(T) {
  List!T list;

  void push(T val) {
    Node!T* node = cast(Node!T*)GC.malloc(Node!T.sizeof, GC.BlkAttr.NO_SCAN);
    node.value   = val;
    node.next    = null;
    list.push(node);
  }

  T pop() {
    Node!T* rt = list.pop;

    if (rt is null) throw new Error("tail is null");
    T rv = rt.value;
    GC.free(rt);
    return rv;
  }
}

minimalStack.d

/*
  Minimal Stack data structure Implementation in D
  
  Copyright (c) 2016 alphaKAI
  This software is released under the MIT License.
*/

import core.memory;

struct Node(T) {
  Node!T* next;
  T       value;
}

struct List(T) {
  Node!T* head = null;

  void push(Node!T* node) {
    if (head is null) {
      head = node;
    } else {
      auto tp   = head;
      head      = node;
      head.next = tp;
    }
  }

  Node!T* pop() {
    if (head is null) {
      return null;
    } else {
      if (head.next is null) {
        auto tp = head;
        head    = null;
        return tp;
      } else {
        auto tp = head;
        head    = tp.next;
        return tp;
      }
    }
  }

  @property bool empty() {
    return head is null;
  }
}

struct Stack(T) {
  List!T list;

  void push(T val) {
    Node!T* node = cast(Node!T*)GC.malloc(Node!T.sizeof, GC.BlkAttr.NO_SCAN);
    node.value   = val;
    node.next    = null;
    list.push(node);
  }

  T pop() {
    Node!T* rt = list.pop;

    if (rt is null) throw new Error("head is null");
    T rv = rt.value;
    GC.free(rt);
    return rv;
  }
}