Infinity alias

[renatocf]

Create an Infinity alias in the same header where Probability is defined, in order to fully encapsulate floating point types in more meaningful definitions.

[igorbonadio]

Should we have an generic Infinity type? Because not all infinities are probabilities...

[igorbonadio]

Or maybe it is better a Zero alias... as -std::numeric_limits<Probability>::infinity() means p(x)=0.

[renatocf]

Hmm... So shouldn't we split our concepts in a Probability and a LogProbability types? I think that would be a more accurate description of what we are using through the system. Or, if all our probabilities are standardized in one of them, then we should use the concept of infinite / zero properly.

Anyway, the idea behind this issue is to use a more semantic representation of what our methods are returning. This will have a direct impact in how assertions shall be made in #50.

[renatocf]

@igorbonadio,

There is a long time we don't discuss this issue. What do you think about it? Does it worth we have a LogProbability alias besides the current Probability class?

I believe my last argument is very reasonable, and I'd like to make this refactoring before going to issue #11. What do you think?

[igorbonadio]

I think we don't need a Probability type because we only use LogProbabilities...

Maybe it is better to rename Probability to LogProbability and create an Infinity type.

[renatocf]

I think this is a good solution. I'll implement it!