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119 lines
4.4 KiB
C++
119 lines
4.4 KiB
C++
// Copyright (c) 2014-2018 Thomas Fussell
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, WRISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE
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//
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// @license: http://www.opensource.org/licenses/mit-license.php
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// @author: see AUTHORS file
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#pragma once
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#include <xlnt/xlnt_config.hpp>
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#include <sstream>
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#include <type_traits>
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namespace xlnt {
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namespace detail {
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/// <summary>
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/// Takes in any number and outputs a string form of that number which will
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/// serialise and deserialise without loss of precision
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/// </summary>
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template <typename Number>
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std::string serialize_number_to_string(Number num)
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{
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// more digits and excel won't match
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constexpr int Excel_Digit_Precision = 15; //sf
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std::stringstream ss;
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ss.precision(Excel_Digit_Precision);
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ss << num;
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return ss.str();
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}
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/// <summary>
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/// constexpr abs
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/// </summary>
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template <typename Number>
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constexpr Number abs(Number val)
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{
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if (val < Number{0})
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{
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return -val;
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}
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return val;
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};
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/// <summary>
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/// constexpr max
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/// </summary>
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template <typename Number>
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constexpr Number max(Number lval, Number rval)
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{
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return (lval < rval) ? rval : lval;
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}
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/// <summary>
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/// constexpr min
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/// </summary>
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template <typename Number>
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constexpr Number min(Number lval, Number rval)
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{
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return (lval < rval) ? lval : rval;
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}
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/// <summary>
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/// Floating point equality requires a bit of fuzzing due to the imprecise nature of fp calculation
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/// References:
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/// - Several blogs/articles were referenced with the following being the most useful
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/// -- https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
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/// -- http://realtimecollisiondetection.net/blog/?p=89
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/// - Testing Frameworks {Catch2, Boost, Google}, primarily for selecting the default scale factor
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/// -- None of these even remotely agree
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/// </summary>
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template <typename EpsilonType = float, // the type to extract epsilon from
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typename LNumber, typename RNumber> // parameter types (deduced)
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bool
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float_equals(const LNumber &lhs, const RNumber &rhs,
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int epsilon_scale = 20) // scale the "fuzzy" equality. Higher value gives a more tolerant comparison
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{
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static_assert(std::is_floating_point<LNumber>::value || std::is_floating_point<RNumber>::value,
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"Using this function with two integers is just wasting time. Use ==");
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static_assert(std::is_floating_point<EpsilonType>::value,
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"Cannot extract epsilon from a number that isn't a floating point type");
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// NANs always compare false with themselves
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if ((lhs != lhs) || (rhs != rhs)) // std::isnan isn't constexpr
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{
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return false;
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}
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// a type that lhs and rhs can agree on
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using common_t = typename std::common_type<LNumber, RNumber>::type;
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// epsilon type defaults to float because even if both args are a higher precision type
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// either or both could have been promoted by prior operations
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// if a higher precision is required, the template type can be changed
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constexpr common_t epsilon = std::numeric_limits<EpsilonType>::epsilon();
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// the "epsilon" then needs to be scaled into the comparison range
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// epsilon for numeric_limits is valid when abs(x) <1.0, scaling only needs to be upwards
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// in particular, this prevents a lhs of 0 from requiring an exact comparison
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// additionally, a scale factor is applied.
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common_t scaled_fuzz = epsilon_scale * epsilon * max(xlnt::detail::abs<common_t>(lhs), common_t{1});
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return ((lhs + scaled_fuzz) >= rhs) && ((rhs + scaled_fuzz) >= lhs);
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}
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} // namespace detail
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} // namespace xlnt
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