fix: 'format_to_n' compiles 'std::back_inserter' arguments #913
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| truncating_iterator& operator++(int) { return *this; } | ||
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| truncating_iterator& operator*() { return *this; } | ||
| }; |
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Is it possible to move common code between the two specializations into a superclass to reduce copy-paste?
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Done ... |
include/fmt/format.h
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| typedef typename OutputIt::container_type::value_type value_type; | ||
| typedef void difference_type; | ||
| typedef void pointer; | ||
| typedef void reference; |
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Why are these void and are they different from their counterparts in iterator_traits?
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void actually is their type in iterator_traits. We are talking about a back_insert_operator here. I've basically just redefined the value_type from void to the value_typeof the underlying container.
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Then they can be moved to truncating_iterator_base I think.
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I agree, even if it loses information about the underlying iterator type. Anyway, I've refactored these three void typedefs into the common base class, the rest must stay as is: these are the essential differences between "regular output iterators" and "back insert interators".
std::back_insert_iterators model the OutputIterator concept but differ considerably in their traits and behavior. In particular the former made compilation to fail when format_to_n is given a back_inserter as first argument. The emulation of an OutputIterator is not perfect due to the behavioural differences of back_insert_iterators (e.g. assignment always implies increment) but good enough to be used within fmt's machinery.
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Merged, thanks! |
std::back_insert_iterators model the OutputIterator concept but differ considerably in their traits and behavior. In particular the former made compilation to fail when format_to_n is given a back_inserter as first argument. The emulation of an OutputIterator is not perfect due to the behavioural differences of back_insert_iterators (e.g. assignment always implies increment) but good enough to be used within fmt's machinery.