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Utility::Debug: add std::ostream output operator call converter #88

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Utility::Debug: add std::ostream output operator call converter #88

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6964c21
Utility::Debug: DebugOstreamFallback enable if has ostream operator
rune-scape Jan 24, 2020
bcc6544
Merge https://github.com/mosra/corrade into pr88
rune-scape Jan 27, 2020
dfa849b
Move DeclareLvalueReference to TypeTraits.h
rune-scape Jan 28, 2020
8b1e935
Utility::Debug: add HasDebugStreamOperator check to DebugOstreamFallback
rune-scape Jan 29, 2020
cf3f6fd
Utility::Debug: added std::ostream output operator call converter.
rune-scape Jan 29, 2020
8b048e6
Utility: doc++
rune-scape Jan 29, 2020
05cfb24
Utility::Debug: OstreamDebug::operator<< is now in its own namespace
rune-scape Feb 2, 2020
3b75172
Utility::Debug: more docs
rune-scape Feb 2, 2020
be5dfa9
Utility: snippet had narrowing conversion
rune-scape Feb 2, 2020
9abf7c3
Utility: DebugTest.cpp: corrected sourceLocation test
rune-scape Feb 2, 2020
b3129ed
Utility: whitespace at EOL.
mosra Feb 5, 2020
07dad62
Utility: this is how it is expected to work.
mosra Feb 5, 2020
ccb7bcd
Utility: eureka!
mosra Feb 5, 2020
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31 changes: 30 additions & 1 deletion src/Corrade/Utility/DebugStl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -103,9 +103,28 @@ template<class ...Args> Debug& operator<<(Debug& debug, const std::tuple<Args...

namespace Implementation {

CORRADE_HAS_TYPE(
HasOstreamOperator,
typename std::enable_if<std::is_same<
decltype(DeclareLvalueReference<std::ostream>() << std::declval<T>()),
std::add_lvalue_reference<std::ostream>::type
>::value>::type
);

CORRADE_HAS_TYPE(
HasDebugStreamOperator,
typename std::enable_if<std::is_same<
decltype(DeclareLvalueReference<Debug>() << std::declval<T>()),
std::add_lvalue_reference<Debug>::type
>::value>::type
);

/* Used by Debug::operator<<(Implementation::DebugOstreamFallback&&) */
struct DebugOstreamFallback {
template<class T> /*implicit*/ DebugOstreamFallback(const T& t): applier(&DebugOstreamFallback::applyImpl<T>), value(&t) {}
template<
class T,
typename = typename std::enable_if<HasOstreamOperator<T>::value && !HasDebugStreamOperator<T>::value>::type
> /*implicit*/ DebugOstreamFallback(const T& t): applier(&DebugOstreamFallback::applyImpl<T>), value(&t) {}

void apply(std::ostream& s) const {
(this->*applier)(s);
Expand All @@ -130,4 +149,14 @@ CORRADE_UTILITY_EXPORT Debug& operator<<(Debug& debug, Implementation::DebugOstr

}}

template<typename T>

@mosra mosra Jan 30, 2020

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One last thing: can you

  • add a short documentation block for this new function,
  • mention this in the class documentation so people get to know it exists -- there's a "Printing STL types" section, so maybe extending that a bit ("Printing STL types, interaction with iostreams"?)
  • and add a test in Test/DebugTest.cpp? There's ostreamFallback and ostreamFallbackPriority, so something similar (ostreamDelegate?) and also similarly checking the priority works for the inverse case, picking the ostream operator over the Debug one -- btw., don't forget to list the two new methods in the addTests() so these get properly called

Thank you! 👍

@rune-scape rune-scape Feb 1, 2020

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yes! wow ostreamDelegate is way better than any name I considered

typename std::enable_if<
Corrade::Utility::Implementation::HasDebugStreamOperator<T>::value && !Corrade::Utility::Implementation::HasOstreamOperator<T>::value,
std::ostream
>::type &operator<<(std::ostream &os, const T &val) {
Corrade::Utility::Debug debug{&os, Corrade::Utility::Debug::Flag::NoNewlineAtTheEnd};
debug << val;
return os;
}

#endif
6 changes: 6 additions & 0 deletions src/Corrade/Utility/TypeTraits.h
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Expand Up @@ -163,4 +163,10 @@ template<class T> using IsStringLike = std::integral_constant<bool,

}}

/**
@brief Like @cpp std::declval @ce, but declares an lvalue reference
*/
template<typename T>
typename std::add_lvalue_reference<T>::type DeclareLvalueReference() noexcept;

@mosra mosra Jan 30, 2020

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Minor: I'm usually not putting a newline after template<..>, keeping the whole signature a single line. (Or generally not adding a newline unless really needed to keep the code vertically terse.)


#endif