id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
10110	boost::random::negative_binomial_distribution unnecessary restriction to IntType for parameter k	Maximilian Kleinert <kleinert.max@…>	No-Maintainer	"Hi.

In the implementation of boost::random::negative_binomial_distribution there is an unnecessary restriction to IntType for parameter k.

A double parameter k will be casted to integer resulting in a different distribution than desired. If one compiles with -Wconversion a warning is given:
warning: conversion to ‘int’ from ‘double’ may alter its value [-Wconversion]
see attached example_file.
This can lead to unwanted realization of a negative binomial distribution for non integer parameters k.

Further there are no assertion checks on the parameters in instantiating a boost::random::negative_binomial_distribution object. These assertions are checked during the sampling process via boost::random::gamma_distribution.
There (and in general for negative binomial distribution) the parameter k must be strictly greater than zero and not as mentioned in the documentation ""Requires: k >=0"".

This can easily be extended by changing IntType to RealType in 5 occurrences regarding the parameter k.

Thank you,
Max

P.S.: I compiled the example file with:
g++ -Wconversion -o negbin_test -std=c++11 negbin_test.cpp"	Bugs	new	To Be Determined	random	Boost 1.55.0	Problem		random, negative binomial distribution