Re: [boost] [random] fix assert in uniform_real.hpp

From: Matthias Troyer (troyer_at_[hidden])
Date: 2007-05-12 21:45:48

On 13 May 2007, at 10:45, Neal Becker wrote:

> Matthias Troyer wrote:
>
>>
>> On 11 May 2007, at 23:13, Neal Becker wrote:
>>
>>> diff -r 5fcada374f41 boost/random/uniform_real.hpp
>>> --- a/boost/random/uniform_real.hpp     Thu May 10 08:59:36 2007  
>>> -0400
>>> +++ b/boost/random/uniform_real.hpp     Fri May 11 11:12:44 2007  
>>> -0400
>>> @@ -40,7 +40,7 @@ public:
>>>  #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
>>>      BOOST_STATIC_ASSERT(! 
>>> std::numeric_limits<RealType>::is_integer);
>>>  #endif
>>> -    assert(min_arg < max_arg);
>>> +    assert(min_arg <= max_arg);
>>>    }
>>>
>>>    // compiler-generated copy ctor and assignment operator are fine
>>
>> This does not make sense to me. uniform_real should create numbers u
>> that are
>>
>> min_arg <= u < maxarg
>>
>> Thus choosing minarg == maxarg does not make sense since the set of
>> possible values would be empty.
>>
> It's a valid limiting case.
>
> Here's the use case:
>
> Your program has a random number generator.  The range is set by  
> command
> line argument.  For test purposes, you set the range to be  
> infinitesimal.
> As it is now, you get the assertion failure.  There is no good  
> reason for
> this to fail, AFAICT.  Allowing it is useful and harmless.

Sorry, the range is not infinitesimal but is empty. What value should  
the generator return when minarg == maxarg? In that case there is no  
legal value. Should the generator check and throw when invoked?

Matthias