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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* This file incorporates work covered by the following license notice:
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed
* with this work for additional information regarding copyright
* ownership. The ASF licenses this file to you under the Apache
* License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.apache.org/licenses/LICENSE-2.0 .
*/
#pragma once
#include "global.hxx"
class SubTotal
{
public:
static bool SafePlus( double& fVal1, double fVal2);
static bool SafeMult( double& fVal1, double fVal2);
static bool SafeDiv( double& fVal1, double fVal2);
};
class ScFunctionData;
/** Implements the Welford Online one-pass algorithm.
See https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_Online_algorithm
and Donald E. Knuth, TAoCP vol.2, 3rd edn., p. 232
*/
class WelfordRunner
{
public:
WelfordRunner() : mfMean(0.0), mfM2(0.0), mnCount(0) {}
void update( double fVal );
sal_uInt64 getCount() const { return mnCount; }
double getVarianceSample() const { return mnCount > 1 ? mfM2 / (mnCount-1) : 0.0; }
double getVariancePopulation() const { return mnCount > 0 ? mfM2 / mnCount : 0.0; }
// The private variables can be abused by ScFunctionData as general
// sum/min/max/ave/count/... variables to reduce memory footprint for that
// ScFunctionData may be a mass object during consolidation.
// ScFunctionData::update() and getResult() take care that purposes are not
// mixed.
friend class ScFunctionData;
private:
double mfMean;
double mfM2;
sal_uInt64 mnCount;
};
/** To calculate a single subtotal function. */
class ScFunctionData
{
public:
ScFunctionData() : meFunc(SUBTOTAL_FUNC_NONE), mbError(false) {}
ScFunctionData( ScSubTotalFunc eFn ) : meFunc(eFn), mbError(false) {}
void update( double fNewVal );
/// Check getError() after (!) obtaining the result.
double getResult();
bool getError() const { return mbError; }
ScSubTotalFunc getFunc() const { return meFunc; }
void setError() { mbError = true; }
private:
WelfordRunner maWelford;
ScSubTotalFunc meFunc;
bool mbError;
double& getValueRef() { return maWelford.mfMean; }
sal_uInt64& getCountRef() { return maWelford.mnCount; }
};
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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