NEW add JKQTPExpected

doc/dox/whatsnew.dox

@@ -27,7 +27,8 @@ Changes, compared to  \ref page_whatsnew_V4_0_0 "v4.0.0" include:
     <li>NEW/BREAKING: provide general targets JKQTPlotter5/6::JKQTPlotter5/6, JKQTPlotter5/6::JKQTMathText5/6, ... which are independent of the type of build (shared/static)</li>    
     <li>NEW/BREAKING: refactor CMake-Code, so static/dynamic switch is done via <code>BUILD_SHARED_LIBS</code>, which retires <code>JKQtPlotter_BUILD_STATIC_LIBS</code>, <code>JKQtPlotter_BUILD_SHARED_LIBS</code> and removes the capability to build static and shared libraries in one location (fixes issue #104)</li>    
     <li>NEW: prepareed library for CMake's <a href="https://cmake.org/cmake/help/latest/module/FetchContent.html">FetchContent</a>-API</li>    
-    <li>NEW: the different sub-libraries JKQTPlotter, JKQTFastPlotter (DEPRECATED), JKQTMath, JKQTMathText can be activated/deactivated with CMake options JKQtPlotter_BUILD_LIB_JKQTPLOTTER, JKQtPlotter_BUILD_LIB_JKQTFASTPLOTTER, JKQtPlotter_BUILD_LIB_JKQTMATHTEXT, JKQtPlotter_BUILD_LIB_JKQTMATH</li>    
+    <li>NEW: the different sub-libraries JKQTPlotter, JKQTFastPlotter (DEPRECATED), JKQTMath, JKQTMathText can be activated/deactivated with CMake options JKQtPlotter_BUILD_LIB_JKQTPLOTTER, JKQtPlotter_BUILD_LIB_JKQTFASTPLOTTER, JKQtPlotter_BUILD_LIB_JKQTMATHTEXT, JKQtPlotter_BUILD_LIB_JKQTMATH</li>   
+    <li>NEW add JKQTPExpected datatype</li>    
   </ul></li>
 
   <li>JKQTPlotter:<ul>

lib/jkqtcommon.pri

@@ -27,7 +27,10 @@ isEmpty(JKQTP_COMMON_PRI_INCLUDED) {
                $$PWD/jkqtcommon/jkqtpenhancedpainter.h \
                $$PWD/jkqtcommon/jkqtphighrestimer.h \
                $$PWD/jkqtcommon/jkqttools.h \
-               $$PWD/jkqtcommon/jkqtpicons.h
+               $$PWD/jkqtcommon/jkqtpicons.h \
+               $$PWD/jkqtcommon/jkqtpcachingtools.h \
+               $$PWD/jkqtcommon/jkqtpconcurrencytools.h \
+               $$PWD/jkqtcommon/jkqtpexpected.h
 
 
 
@@ -41,7 +44,9 @@ isEmpty(JKQTP_COMMON_PRI_INCLUDED) {
                $$PWD/jkqtcommon/jkqtpenhancedpainter.cpp \
                $$PWD/jkqtcommon/jkqtphighrestimer.cpp \
                $$PWD/jkqtcommon/jkqttools.cpp \
-               $$PWD/jkqtcommon/jkqtpicons.cpp
+               $$PWD/jkqtcommon/jkqtpicons.cpp \
+               $$PWD/jkqtcommon/jkqtpcachingtools.cpp \
+               $$PWD/jkqtcommon/jkqtpconcurrencytools.cpp 
 
 
     INCLUDEPATH += $$PWD

lib/jkqtcommon/CMakeLists.txt

@@ -47,6 +47,7 @@ target_sources(${lib_name} PUBLIC FILE_SET HEADERS TYPE HEADERS
     jkqtpgeometrytools.h
     jkqtpconcurrencytools.h
     jkqtpcachingtools.h
+    jkqtpexpected.h
 )
 
 

lib/jkqtcommon/jkqtpexpected.h

@@ -0,0 +1,84 @@
+
+/*
+    Copyright (c) 2008-2024 Jan W. Krieger (<jan@jkrieger.de>)
+
+    
+
+    This software is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef JKQTPEXPECTED_H_INCLUDED
+#define JKQTPEXPECTED_H_INCLUDED
+
+#include <exception>
+
+
+/** \brief tag type for an unexpected/error result in JKQTPExpected
+ *  \ingroup jkqtptools_general
+ *
+ *  \see JKQTPExpected, JKQTPUnexpected
+ */
+struct JKQTPExpectedUnexpectedType {};
+/** \brief tag for an unexpected/error result in JKQTPExpected
+ *  \ingroup jkqtptools_general
+ *
+ *  \see JKQTPExpected, JKQTPExpectedUnexpectedType
+ */
+inline constexpr JKQTPExpectedUnexpectedType JKQTPUnexpected {};
+
+/** \brief an "expected" datatype, which can either represent a function result of type \c T or an error of type \c E
+ *  \ingroup jkqtptools_general
+ *
+ *  Usage example:
+ *  \code
+ *    JKQTPExpected<double,QString> toInt(QString s) {
+ *      bool ok=false;
+ *      int i=s.toInt(&ok);
+ *      if (ok) return {i}
+ *      else return { JKQTPUnexpected, QString("cannot convert to int") };
+ *    }
+ *
+ *    auto r=toInt("1.0a");
+ *    if (r.hasValue()) qDebug()<<"SUCCESS! i="<<r.value();
+ *    else qDebug()<<"FAILURE: "<<r.error();
+ *  \endcode
+ *
+ *
+ *  \see JKQTPExpectedUnexpectedType, JKQTPUnexpected
+ */
+template<class T, class E>
+struct JKQTPExpected {
+    JKQTPExpected()=delete;
+    JKQTPExpected(const T& value_): m_hasValue(true), m_value(value_), m_error() {};
+    JKQTPExpected(const JKQTPExpected<T,E>& other)=default;
+    JKQTPExpected(JKQTPExpectedUnexpectedType, const E& error_): m_hasValue(false), m_value(), m_error(error_) {};
+
+    const T& value() const {
+        if (m_hasValue) return m_value;
+        throw std::runtime_error("value not available");
+    }
+    const E& error() const {
+        if (!m_hasValue) return m_error;
+        throw std::runtime_error("error not available");
+    }
+    const bool has_value() const { return m_hasValue; }
+    operator bool() const { return m_hasValue; }
+private:
+    const bool m_hasValue;
+    const E m_error;
+    const T m_value;
+};
+
+
+#endif // JKQTPEXPECTED_H_INCLUDED