mirror of
https://github.com/jkriege2/JKQtPlotter.git
synced 2024-11-15 18:15:52 +08:00
85 lines
2.6 KiB
C
85 lines
2.6 KiB
C
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/*
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Copyright (c) 2008-2024 Jan W. Krieger (<jan@jkrieger.de>)
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This software is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef JKQTPEXPECTED_H_INCLUDED
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#define JKQTPEXPECTED_H_INCLUDED
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#include <exception>
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/** \brief tag type for an unexpected/error result in JKQTPExpected
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* \ingroup jkqtptools_general
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*
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* \see JKQTPExpected, JKQTPUnexpected
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*/
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struct JKQTPExpectedUnexpectedType {};
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/** \brief tag for an unexpected/error result in JKQTPExpected
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* \ingroup jkqtptools_general
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*
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* \see JKQTPExpected, JKQTPExpectedUnexpectedType
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*/
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inline constexpr JKQTPExpectedUnexpectedType JKQTPUnexpected {};
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/** \brief an "expected" datatype, which can either represent a function result of type \c T or an error of type \c E
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* \ingroup jkqtptools_general
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*
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* Usage example:
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* \code
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* JKQTPExpected<double,QString> toInt(QString s) {
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* bool ok=false;
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* int i=s.toInt(&ok);
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* if (ok) return {i}
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* else return { JKQTPUnexpected, QString("cannot convert to int") };
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* }
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*
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* auto r=toInt("1.0a");
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* if (r.hasValue()) qDebug()<<"SUCCESS! i="<<r.value();
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* else qDebug()<<"FAILURE: "<<r.error();
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* \endcode
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*
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*
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* \see JKQTPExpectedUnexpectedType, JKQTPUnexpected
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*/
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template<class T, class E>
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struct JKQTPExpected {
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JKQTPExpected()=delete;
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JKQTPExpected(const T& value_): m_hasValue(true), m_value(value_), m_error() {};
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JKQTPExpected(const JKQTPExpected<T,E>& other)=default;
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JKQTPExpected(JKQTPExpectedUnexpectedType, const E& error_): m_hasValue(false), m_value(), m_error(error_) {};
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const T& value() const {
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if (m_hasValue) return m_value;
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throw std::runtime_error("value not available");
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}
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const E& error() const {
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if (!m_hasValue) return m_error;
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throw std::runtime_error("error not available");
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}
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const bool has_value() const { return m_hasValue; }
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operator bool() const { return m_hasValue; }
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private:
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const bool m_hasValue;
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const E m_error;
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const T m_value;
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};
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#endif // JKQTPEXPECTED_H_INCLUDED
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