1[/ 2 Copyright 2010 Neil Groves 3 Distributed under the Boost Software License, Version 1.0. 4 (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 5/] 6[section:type_erased type_erased] 7 8[table 9 [[Syntax] [Code]] 10 [[Pipe] [`rng | boost::adaptors::type_erased<Value, Traversal, Reference, Difference, Buffer>()`]] 11 [[Function] [`boost::adaptors::type_erase(rng, boost::adaptors::type_erased<Value, Traversal, Reference, Difference, Buffer>)`]] 12] 13 14Please note that it is frequently unnecessary to use the `type_erased` adaptor. It is often better to use the implicit conversion to `any_range`. 15 16Let `Rng` be the type of `rng`. 17 18* [*Template parameters:] 19 * `Value` is the `value_type` for the `any_range`. If this is set to boost::use_default, `Value` will be calculated from the 20 range type when the adaptor is applied. 21 * `Traversal` is the tag used to identify the traversal of the resultant range. Frequently it is desirable to set a traversal category lower than the source container or range to maximize the number of ranges that can convert to the `any_range`. If this is left as boost::use_default then `Traversal` will be `typename boost::iterator_traversal<boost::range_iterator<Rng>::type>::type` 22 * `Reference` is the `reference` for the `any_range`. `boost::use_default` will equate to `typename range_reference<Rng>::type`. 23 * `Difference` is the `difference_type` for the any_range. `boost::use_default` will equate to `typename boost::range_difference<Rng>::type` 24 * `Buffer` is the storage used to allocate the underlying iterator wrappers. This can typically be ignored, but is available as a template parameter for customization. Buffer must be a model of the `AnyIteratorBufferConcept`. 25* [*Precondition:] `Traversal` is one of `{ boost::use_default, boost::single_pass_traversal_tag, boost::forward_traversal_tag, boost::bidirectional_traversal_tag, boost::random_access_traversal_tag }` 26* [*Returns:] The returned value is the same as `typename any_range_type_generator< Rng, Value, Traversal, Reference, Difference, Buffer >` that represents `rng` in a type-erased manner. 27* [*Range Category:] __single_pass_range__ 28* [*Returned Range Category:] if `Traversal` was specified as `boost::use_default` then `typename boost::iterator_traversal<boost::range_iterator<Rng>::type>::type`, otherwise `Traversal`. 29 30[heading AnyIteratorBufferConcept] 31`` 32class AnyIteratorBufferConcept 33{ 34public: 35 AnyIteratorBufferConcept(); 36 ~AnyIteratorBufferConcept(); 37 38 // bytes is the requested size to allocate. This function 39 // must return a pointer to an adequate area of memory. 40 // throws: bad_alloc 41 // 42 // The buffer will only ever have zero or one 43 // outstanding memory allocations. 44 void* allocate(std::size_t bytes); 45 46 // deallocate this buffer 47 void deallocate(); 48}; 49`` 50 51[section:type_erased_example type-erased example] 52[import ../../../test/adaptor_test/type_erased_example.cpp] 53[type_erased_example] 54[endsect] 55 56This would produce the output: 57`` 581,2,3,4,5, 596,7,8,9,10, 6011,12,13,14,15, 6111,12,13,14,15, 62`` 63[endsect] 64 65 66