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### 871. Iota's requirements on `T` are too strong

Section: 27.10.13 [numeric.iota] Status: C++11 Submitter: Daniel Krügler Opened: 2008-08-20 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

According to the recent WP N2691, 27.10.13 [numeric.iota]/1, the requires clause of `std::iota` says:

> `T` shall meet the requirements of `CopyConstructible` and `Assignable` types, and shall be convertible to `ForwardIterator`'s value type.[..]

Neither `CopyConstructible` nor `Assignable` is needed, instead `MoveConstructible` seems to be the correct choice. I guess the current wording resulted as an artifact from comparing it with similar numerical algorithms like `accumulate`.

Note: If this function will be conceptualized, the here proposed `MoveConstructible` requirement can be removed, because this is an implied requirement of function arguments, see N2710/[temp.req.impl]/3, last bullet.

[ post San Francisco: ]

> Issue pulled by author prior to review.

[ 2009-07-30 Daniel reopened: ]

> with the absence of concepts, this issue (closed) is valid again and I suggest to reopen it. I also revised by proposed resolution based on N2723 wording:

[ 2009-10 Santa Cruz: ]

> Change 'convertible' to 'assignable', Move To Ready.

Proposed resolution:

Change the first sentence of 27.10.13 [numeric.iota]/1:

> Requires: `T` shall meet the requirements of `CopyConstructible` and `Assignable` types, and shall be assignable to `ForwardIterator`'s value type. [..]