ArgTraits.h
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* file: ArgTraits.h
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* Copyright (c) 2007, Daniel Aarno, Michael E. Smoot .
* Copyright (c) 2017 Google LLC
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// This is an internal tclap file, you should probably not have to
// include this directly
#ifndef TCLAP_ARGTRAITS_H
#define TCLAP_ARGTRAITS_H
namespace TCLAP {
// We use two empty structs to get compile type specialization
// function to work
struct ValueLike {
typedef ValueLike ValueCategory;
virtual ~ValueLike() {}
};
struct StringLike {
virtual ~StringLike() {}
};
struct StringLikeTrait {
typedef StringLike ValueCategory;
virtual ~StringLikeTrait() {}
};
struct ValueLikeTrait {
typedef ValueLike ValueCategory;
virtual ~ValueLikeTrait() {}
};
template<typename T>
class ArgTraits {
// This is a bit silly, but what we want to do is:
// 1) If there exists a specialization of ArgTraits for type X,
// use it.
//
// 2) If no specialization exists but X has the typename
// X::ValueCategory, use the specialization for X::ValueCategory.
//
// 3) If neither (1) nor (2) defines the trait, use the default
// which is ValueLike.
// This is the "how":
//
// test<T>(0) (where 0 is the NULL ptr) will match
// test(typename C::ValueCategory*) iff type T has the
// corresponding typedef. If it does not test(...) will be
// matched. This allows us to determine if T::ValueCategory
// exists by checking the sizeof for the test function (return
// value must have different sizeof).
template<typename C> static short test(typename C::ValueCategory*);
template<typename C> static long test(...);
static const bool hasTrait = sizeof(test<T>(0)) == sizeof(short);
template <typename C, bool>
struct DefaultArgTrait {
typedef ValueLike ValueCategory;
};
template <typename C>
struct DefaultArgTrait<C, true> {
typedef typename C::ValueCategory ValueCategory;
};
public:
typedef typename DefaultArgTrait<T, hasTrait>::ValueCategory ValueCategory;
};
} // namespace
#endif
TCLAP::ArgTraits
Arg traits are used to get compile type specialization when parsing argument values.
Definition: ArgTraits.h:82
TCLAP::ArgTraits::ValueCategory
DefaultArgTrait< T, hasTrait >::ValueCategory ValueCategory
Definition: ArgTraits.h:116
TCLAP
Definition: Arg.h:48
TCLAP::StringLikeTrait
A class can inherit from this object to make it have string like traits.
Definition: ArgTraits.h:58
TCLAP::StringLikeTrait::ValueCategory
StringLike ValueCategory
Definition: ArgTraits.h:59
TCLAP::StringLikeTrait::~StringLikeTrait
virtual ~StringLikeTrait()
Definition: ArgTraits.h:60
TCLAP::StringLike
A string like argument value type is a value that can be set using operator=(string).
Definition: ArgTraits.h:49
TCLAP::StringLike::~StringLike
virtual ~StringLike()
Definition: ArgTraits.h:50
TCLAP::ValueLikeTrait
A class can inherit from this object to make it have value like traits.
Definition: ArgTraits.h:68
TCLAP::ValueLikeTrait::~ValueLikeTrait
virtual ~ValueLikeTrait()
Definition: ArgTraits.h:70
TCLAP::ValueLikeTrait::ValueCategory
ValueLike ValueCategory
Definition: ArgTraits.h:69
TCLAP::ValueLike
A value like argument value type is a value that can be set using operator>>.
Definition: ArgTraits.h:39
TCLAP::ValueLike::ValueCategory
ValueLike ValueCategory
Definition: ArgTraits.h:40
TCLAP::ValueLike::~ValueLike
virtual ~ValueLike()
Definition: ArgTraits.h:41