tpl_scope.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
#ifndef TPL_SCOPE_H
#define TPL_SCOPE_H
 
#include <concepts>
#include <cstddef>
#include <utility>
 
#include <ah-errors.H>
#include <tpl_dynArray.H>
 
namespace Aleph {
template <typename Key, typename Value>
  requires std::equality_comparable<Key>
class Scope
{
public:
  struct Binding
  {
    Key key;      
    Value value;  
  };
 
private:
  struct Frame
  {
    DynArray<Binding> bindings;
  };
 
  DynArray<Frame> frames;
 
  static Value *find_value(DynArray<Binding> &bindings, const Key &key) noexcept
  {
    for (size_t i = bindings.size(); i > 0; --i)
      if (bindings.access(i - 1).key == key)
        return &bindings.access(i - 1).value;
    return nullptr;
  }
 
  static const Value *find_value(const DynArray<Binding> &bindings, const Key &key) noexcept
  {
    for (size_t i = bindings.size(); i > 0; --i)
      if (bindings.access(i - 1).key == key)
        return &bindings.access(i - 1).value;
    return nullptr;
  }
 
  Frame &current_frame()
  {
    ah_runtime_error_unless(frames.size() > 0) << "Scope::current_frame(): no active scope";
    return frames.top();
  }
 
  const Frame &current_frame() const
  {
    ah_runtime_error_unless(frames.size() > 0) << "Scope::current_frame(): no active scope";
    return frames.top();
  }
 
public:
  Scope() = default;
 
  [[nodiscard]] size_t depth() const noexcept
  {
    return frames.size();
  }
 
  [[nodiscard]] bool empty() const noexcept
  {
    return frames.is_empty();
  }
 
  void clear() noexcept
  {
    frames.clear();
  }
 
  size_t enter_scope()
  {
    // Reinitialize reused slots explicitly because DynArray::pop() moves the
    // last frame out before shrinking, and a later append may reuse that
    // moved-from storage.
    frames.append(Frame());
    return frames.size();
  }
 
  void leave_scope()
  {
    ah_runtime_error_unless(frames.size() > 0) << "Scope::leave_scope(): no active scope";
    (void) frames.pop();
  }
 
  bool insert(const Key &key, const Value &value)
  {
    auto &frame = current_frame();
    if (find_value(frame.bindings, key) != nullptr)
      return false;
    frame.bindings.append({key, value});
    return true;
  }
 
  bool insert(Key &&key, Value &&value)
  {
    auto &frame = current_frame();
    if (find_value(frame.bindings, key) != nullptr)
      return false;
    frame.bindings.append({std::move(key), std::move(value)});
    return true;
  }
 
  Value *lookup_local(const Key &key) noexcept
  {
    if (frames.is_empty())
      return nullptr;
    return find_value(frames.top().bindings, key);
  }
 
  const Value *lookup_local(const Key &key) const noexcept
  {
    if (frames.is_empty())
      return nullptr;
    return find_value(frames.top().bindings, key);
  }
 
  Value *lookup(const Key &key) noexcept
  {
    for (size_t i = frames.size(); i > 0; --i)
      if (auto *value = find_value(frames.access(i - 1).bindings, key); value != nullptr)
        return value;
    return nullptr;
  }
 
  const Value *lookup(const Key &key) const noexcept
  {
    for (size_t i = frames.size(); i > 0; --i)
      if (const auto *value = find_value(frames.access(i - 1).bindings, key); value != nullptr)
        return value;
    return nullptr;
  }
};
}  // namespace Aleph
 
#endif  // TPL_SCOPE_H