Difference between revisions of "cpp/named req/OutputIterator"
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!Expression||Return||Equivalent expression||Post-conditions||Notes | !Expression||Return||Equivalent expression||Post-conditions||Notes | ||
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| − | |{{c|*r {{=}} o}}|| || || {{tt|r}} is incrementable || {{tt|r}} | + | |{{c|*r {{=}} o}}|| || || {{tt|r}} is incrementable || {{tt|r}} (along with all copies of {{tt|r}}) is not required to be dereferencable after this operation: it may not be possible to write through the same iterator value twice |
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|{{c|++r}}||{{c|X&}}|| | |{{c|++r}}||{{c|X&}}|| | ||
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|{{c|*r++ {{=}} o}} || || | |{{c|*r++ {{=}} o}} || || | ||
| {{tt|r}} is incrementable | | {{tt|r}} is incrementable | ||
| − | | {{tt|r}} is not required to be dereferencable after this operation. | + | | {{tt|r}} (along with all copies of {{tt|r}}) is not required to be dereferencable after this operation. |
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Equality and inequality may not be defined for output iterators. | Equality and inequality may not be defined for output iterators. | ||
| − | Assignment through the same value of | + | Assignment through the same value of an output iterator happens only once: algorithms on output iterators must be single-pass algorithms. |
Examples of output iterators that are not forward iterators are {{lc|std::ostream_iterator}} and {{lc|std::ostreambuf_iterator}}. | Examples of output iterators that are not forward iterators are {{lc|std::ostream_iterator}} and {{lc|std::ostreambuf_iterator}}. | ||
Revision as of 05:39, 22 August 2014
Template:cpp/concept/title Template:cpp/concept/navbar
An OutputIterator is an Template:concept that can write to the pointed-to element.
An example of a type that implements OutputIterator is std::ostream_iterator.
When Template:concept, Template:concept, or Template:concept satisfies the Template:concept requirements in addition to its own requirements, it is described as mutable.
Requirements
The type X satisfies OutputIterator if
- The type
Xsatisfies Template:concept -
Tis a class type or a pointer type
And, given
-
oa value of some type that is writable to the output iterator -
ran lvalue of typeX,
The following expressions must be valid and have their specified effects
| Expression | Return | Equivalent expression | Post-conditions | Notes |
|---|---|---|---|---|
| *r = o | r is incrementable |
r (along with all copies of r) is not required to be dereferencable after this operation: it may not be possible to write through the same iterator value twice
| ||
| ++r | X& | &r == &++r, r is incrementable
|
r is not required to be dereferencable after this operation.
| |
| r++ | convertible to const X& | X temp = r; ++r; |
r is incrementable
| |
| *r++ = o | r is incrementable
|
r (along with all copies of r) is not required to be dereferencable after this operation.
|
Notes
The only valid use of operator* with an output iterator is on the left of an assignment.
Equality and inequality may not be defined for output iterators.
Assignment through the same value of an output iterator happens only once: algorithms on output iterators must be single-pass algorithms.
Examples of output iterators that are not forward iterators are std::ostream_iterator and std::ostreambuf_iterator.
