[REVIEW] Custom assertions

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Summary

The custom assertions should be as simple as possible, follow the single responsibility principle, have descriptive names. The error messages should be informative and the corresponding variables should follow a naming convention.

Checklist

Miscellaneous assertions

• is_positive_number: Tests if a number is scalar and positive; not contained in assertthat-package
• is_nonnegative_number: Tests if a number is scalar and non-negative; not contained in assertthat-package

Discribution assertions

• is_dimension: Tests if a number is a natural number larger than 1

Marshall--Olkin assertions

• is_32bit_complient_dimension: Tests if a dimension for a Marshall--Olkin distribution is 32-bit compliant, i.e. if the number of distribution parameters will not exceed the 32-bit limit.
• is_mo_parameter: Tests if a parameter vector of shock rates is a valid Marshall--Olkin parameter vector, i.e. if it has the correct length, all elements are non-negative numbers, and if the resulting marginal rates are positive.
• is_ex_mo_parameter: Tests if a parameter vector of shock rates is a valid Marshall--Olkin parameter vector, i.e. if it has the correct length, all elements are non-negative numbers, and if the resulting marginal rate is positive.
• is_lfm_cpp_param: Tests if a parameter list is a valid parameterisation of a Levy-frailty Marshall--Olkin model, i.e. if the rate, drift, and killing parameters are non-negative numbers and sum up to a positive number and if jump distribution is correctly parametrised.

Jump distribution assertions

• is_rjump_name: Tests if the given name is a valid method to simulate jumps; jump distributions are currently limited to exponential and fixed jump distributions.
• is_rjump_param: Tests if the given parameter list is valid for the given method name by performing a test run (warning: this might change the RNG state).

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• Implement an assertion is_cuadras_auge_param which tests if a parametrisation for the Cuadras-Augé distribution is valid, i.e. if alpha and beta are non-negative numbers and if their sum is positive.

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There should be some structural changes to the custom assertions:

• use always _parameter instead of param
• remove redundant roxygen2 comments (code should only be explained if it is not self-explanatory).
• use only one error message template for all parameter error messages.

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• assertions should not use || or && if not necessary.

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• rename is_lfm_cpp_parameter to is_lfm_cpp_mo_parameter

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• modify is_rjump_parameter is rump parameter such that the RNG state is not changed