Re: [boost] [math distributions] where to check for validity of distribution variables?

Subject: Re: [boost] [math distributions] where to check for validity of distribution variables?
From: John Maddock (john_at_[hidden])
Date: 2008-11-22 14:33:33

Thijs van den Berg wrote:
>> ah! you're saying you van have one type of policy for the
>> distribution (construtor) and another policy
>> type in some non-member function like pdf.
>> that explains the things I'm seeing!

Nope, the policy that the distribution has applies to all the non-member 
functions as well, it's just that the *error handlers may not throw, but 
return an error value instead*.

>> A final question regarding the error checking is this:
>> Suppose a distribution has a couple of valid an invalid parameters.
>> E.g. normal(2,0),  whith has a valid
>> mean=2 and invalid std=0. Formally that would make the distribution
>> object invalid... There are at least
>> two possible view on what to do with non-member fuctions.
>> 1) Make *all* of them return NaN because the distribution in invalid.
>> This is a mathematical interpretation
>> or
>> 2) (current implementation) try to give an answer when possible,
>> this is
>> a "can we calculate the result?"
>> interpretation. In this case we can calculate the mean (it's 2), but
>> we
>> can't calculate the pdf because
>> that would give an divide by zero.
>>
>> I'm asking this because I'd like to stick to you're approach with new
>> code, and *not* because I want
>> to discuss a preference for any of the two... :)

Ah, OK, in that case, let's continue with the status quo :-)

John.