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5d4ffbf2db
This allows new types to be added without any fuzz (no need to specify the traits) if it has operator>>. It also removes the need to manually specify the ArgTrait for all built in types (such as long, bool, char, float etc). ArgTraits now works in the following way: 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.
121 lines
3.7 KiB
C++
121 lines
3.7 KiB
C++
// -*- Mode: c++; c-basic-offset: 4; tab-width: 4; -*-
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/******************************************************************************
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*
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* file: ArgTraits.h
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*
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* Copyright (c) 2007, Daniel Aarno, Michael E. Smoot .
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* All rights reverved.
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*
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* See the file COPYING in the top directory of this distribution for
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* more information.
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*
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* THE SOFTWARE IS PROVIDED _AS IS_, WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*
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*****************************************************************************/
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// This is an internal tclap file, you should probably not have to
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// include this directly
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#ifndef TCLAP_ARGTRAITS_H
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#define TCLAP_ARGTRAITS_H
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namespace TCLAP {
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// We use two empty structs to get compile type specialization
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// function to work
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/**
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* A value like argument value type is a value that can be set using
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* operator>>. This is the default value type.
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*/
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struct ValueLike {
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typedef ValueLike ValueCategory;
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virtual ~ValueLike() {}
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};
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/**
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* A string like argument value type is a value that can be set using
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* operator=(string). Usefull if the value type contains spaces which
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* will be broken up into individual tokens by operator>>.
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*/
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struct StringLike {
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virtual ~StringLike() {}
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};
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/**
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* A class can inherit from this object to make it have string like
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* traits. This is a compile time thing and does not add any overhead
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* to the inherenting class.
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*/
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struct StringLikeTrait {
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typedef StringLike ValueCategory;
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virtual ~StringLikeTrait() {}
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};
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/**
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* A class can inherit from this object to make it have value like
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* traits. This is a compile time thing and does not add any overhead
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* to the inherenting class.
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*/
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struct ValueLikeTrait {
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typedef ValueLike ValueCategory;
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virtual ~ValueLikeTrait() {}
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};
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/**
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* Arg traits are used to get compile type specialization when parsing
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* argument values. Using an ArgTraits you can specify the way that
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* values gets assigned to any particular type during parsing. The two
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* supported types are StringLike and ValueLike. ValueLike is the
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* default and means that operator>> will be used to assign values to
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* the type.
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*/
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template<typename T>
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class ArgTraits {
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// This is a bit silly, but what we want to do is:
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// 1) If there exists a specialization of ArgTraits for type X,
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// use it.
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//
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// 2) If no specialization exists but X has the typename
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// X::ValueCategory, use the specialization for X::ValueCategory.
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//
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// 3) If neither (1) nor (2) defines the trait, use the default
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// which is ValueLike.
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// This is the "how":
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//
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// test<T>(0) (where 0 is the NULL ptr) will match
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// test(typename C::ValueCategory*) iff type T has the
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// corresponding typedef. If it does not test(...) will be
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// matched. This allows us to determine if T::ValueCategory
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// exists by checking the sizeof for the test function (return
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// value must have different sizeof).
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template<typename C> static short test(typename C::ValueCategory*);
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template<typename C> static long test(...);
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static const bool hasTrait = sizeof(test<T>(0)) == sizeof(short);
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template <typename C, bool>
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struct DefaultArgTrait {
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typedef ValueLike ValueCategory;
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};
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template <typename C>
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struct DefaultArgTrait<C, true> {
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typedef typename C::ValueCategory ValueCategory;
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};
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public:
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typedef typename DefaultArgTrait<T, hasTrait>::ValueCategory ValueCategory;
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};
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#endif
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} // namespace
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