Ichthyostega
d29e4e2d6f
we have a catch-all template operator to get a string converted or pretty printed output from "any object". Unfortunately this overload counts equivalent to another overload by the IO manipulators. Solution is to define both operarators similar in the first argument, thus turing the overload for the IO manipulators into the more specific overload due to the explicitly given second argument
104 lines
3.6 KiB
C++
104 lines
3.6 KiB
C++
/*
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FORMAT-COUT.hpp - use custom string conversions in stream output
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Copyright (C) Lumiera.org
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2016, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (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 General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/** @file format-cout.hpp
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** Automatically use custom string conversion in C++ stream output.
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** This diagnostics facility allows just to dump any object into `cout` or `cerr`.
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** Pointers will be detected, checked for NULL and printed as address, followed
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** by the representation of the pointee. When the displayed entity defines an
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** `operator string()`, this custom string conversion will be used (suppressing
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** any exceptions, of course). As fallback, a simplified type string is printed.
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**
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** \par policy
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** What shall be expected from a generic toString conversion?
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** It should be _minimal_, it should be _transparent_ and it should
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** always work and deliver a string, irrespective of the circumstances.
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** By extension, this means that we do not want to differentiate much
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** between values, references and pointers, which also means, we do
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** not want to indicate pointers explicitly (just signal NULL, when
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** encountered). The situation is slightly different for the `ostream`
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** inserter; in a modern GUI application, there isn't much use for
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** STDOUT and STDERR, beyond error messages and unit testing.
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** Thus, we can strive at building a more convenient flavour
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** here, which does indeed even show the address of pointers.
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**
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** @see FormatCOUT_test
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** @see FormatHelper_test
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** @see [generic string conversion helper](\ref util::toString() )
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** @see [frontend for boost::format, printf-style](format-string.hpp)
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**
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*/
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#ifndef LIB_FORMAT_COUT_H
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#define LIB_FORMAT_COUT_H
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#include "lib/format-obj.hpp"
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#include <string>
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#include <iostream>
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// make those generally visible
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using std::cout;
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using std::cerr;
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using std::endl;
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namespace std {
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namespace { // toggle for the following generic overloads of operator<<
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template<typename X>
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using enable_StringConversion = lib::meta::enable_if< lib::meta::use_StringConversion4Stream<X>>;
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}
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/** generic overload to use custom string conversions in output */
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template<typename _CharT, typename _Traits, typename X, typename = enable_StringConversion<X>>
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inline basic_ostream<_CharT, _Traits>&
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operator<< (basic_ostream<_CharT, _Traits>& os, X const& obj)
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{
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return os << util::StringConv<X>::invoke (obj);
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}
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/** generic overload to pretty-print any pointer in output
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* @note possibly also invokes custom string conversion,
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* in case the pointee defines one
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*/
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template<typename _CharT, typename _Traits, typename X, typename = enable_StringConversion<X>>
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inline basic_ostream<_CharT, _Traits>&
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operator<< (basic_ostream<_CharT, _Traits>& os, X const* ptr)
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{
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if (ptr)
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return util::showAddr(os, ptr) << " ↗" << util::StringConv<X>::invoke (*ptr);
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else
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return os << "⟂ «" << lib::meta::typeStr<X>() << "»";
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}
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} // namespace std
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#endif /*LIB_FORMAT_COUT_H*/
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