54 lines
1.1 KiB
C++
54 lines
1.1 KiB
C++
//
|
|
// immer: immutable data structures for C++
|
|
// Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente
|
|
//
|
|
// This software is distributed under the Boost Software License, Version 1.0.
|
|
// See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt
|
|
//
|
|
|
|
#pragma once
|
|
|
|
#include "dada.hpp"
|
|
|
|
namespace {
|
|
|
|
template <typename VP, typename VT>
|
|
struct transient_tester
|
|
{
|
|
VP vp;
|
|
VT vt;
|
|
dadaism d = {};
|
|
bool transient = false;
|
|
|
|
transient_tester(VP vp)
|
|
: vp{vp}
|
|
, vt{vp.transient()}
|
|
{}
|
|
|
|
bool step()
|
|
{
|
|
auto s = d.next();
|
|
if (soft_dada()) {
|
|
auto new_transient = !transient;
|
|
try {
|
|
if (new_transient)
|
|
vt = vp.transient();
|
|
else
|
|
vp = vt.persistent();
|
|
} catch (const dada_error&) {
|
|
return false;
|
|
}
|
|
transient = new_transient;
|
|
return true;
|
|
} else
|
|
return false;
|
|
}
|
|
};
|
|
|
|
template <typename VP>
|
|
transient_tester<VP, typename VP::transient_type> as_transient_tester(VP p)
|
|
{
|
|
return {std::move(p)};
|
|
}
|
|
|
|
} // anonymous namespace
|