Title
Comment on [rand.dist.samp.pconst]
Status
nad
Section
[rand.dist.samp.pconst]
Submitter
Stephan Tolksdorf

Created on 2007-09-21.00:00:00 last changed 163 months ago

Messages

Date: 2010-10-21.18:28:33

[ Stephan Tolksdorf adds pre-Bellevue: ]

In [rand.dist.samp.pconst]:

Proposed wording a)

Change in para. 2

Constructs a piecewise_constant_distribution object with n = 1, p0 = w0 = 1, b0 = 0, and b1 = 1

and change in para. 5

A vector<result_type> whose size member returns n and whose operator[] member returns pk the weight wk as a double value when invoked with argument k for k = 0, ..., n-1

Proposed wording b)

Change both occurrences of

"piecewise_constant_distribution(InputIteratorB firstB, InputIteratorB lastB,
                                 InputIteratorW firstW, InputIteratorW lastW)

and change in para. 3

the length of the sequence w starting from firstW shall be at least n, *firstW shall return a value w0 that is convertible to double, and any wk for k >= n shall be ignored by the distribution [firstW, lastW) shall form a sequence w of length n whose leading element w0 shall be convertible to double

Date: 2010-10-21.18:28:33

Proposed resolution:

See N2424 for the proposed resolution.

Date: 2010-10-21.18:28:33

[ Bellevue: ]

In N2424. There is already precedent elsewhere in the library. Follows existing convention. NAD.

Date: 2010-10-21.18:28:33

[ Stephan Tolksdorf adds pre-Bellevue: ]

In reply to the discussion in N2424 I'd like to make the same comments as for 736.

Date: 2007-09-21.00:00:00
  1. The discussion in point T11 above regarding probabilities() similarly applies to the method densities() of piecewise_constant_distribution.
  2. The design of the constructor

    template <class InputIteratorB, class InputIteratorW> 
    piecewise_constant_distribution( InputIteratorB firstB, InputIteratorB lastB, 
                                     InputIteratorW firstW);
    

    is unnecessarily unsafe, as there is no separate end-iterator given for the weights. I can't see any performance or convenience reasons that would justify the risks inherent in such a function interface, in particular the risk that input error might go unnoticed.

Possible resolution: I propose to add an InputIteratorW lastW argument to the interface.

History
Date User Action Args
2010-10-21 18:28:33adminsetmessages: + msg3610
2010-10-21 18:28:33adminsetmessages: + msg3609
2010-10-21 18:28:33adminsetmessages: + msg3608
2010-10-21 18:28:33adminsetmessages: + msg3607
2007-09-21 00:00:00admincreate