Checks that data matches a concept
check.scalar.probability(x)
check.positive.scalar(x)
check.nonnegative.scalar(x)
check.probability.distribution(x)
check.scalar.integer(x)
check.scalar.boolean(x)
An object to be checked.
Steven L. Scott steve.the.bayesian@gmail.com
If the object does not match the concept being checked,
stop is called. Otherwise TRUE is returned.