checkmate: Fast Argument Checks for Defensive R Programming

摘要

Dynamically typed programming languages like R allow programmers to writegeneric, flexible and concise code and to interact with the language using aninteractive Read-eval-print-loop (REPL). However, this flexibility has itsprice: As the R interpreter has no information about the expected variabletype, many base functions automatically convert the input instead of raising anexception. Unfortunately, this frequently leads to runtime errors deeper downthe call stack which obfuscates the original problem and renders debuggingchallenging. Even worse, unwanted conversions can remain undetected and skew orinvalidate the results of a statistical analysis. As a resort, assertions canbe employed to detect unexpected input during runtime and to signalunderstandable and traceable errors. The package "checkmate" provides a plethora of functions to check the typeand related properties of the most frequently used R objects and variabletypes. The package is mostly written in C to avoid any unnecessary performanceoverhead. Thus, the programmer can conveniently write concise, well-testedassertions which outperforms custom R code for many applications. Furthermore,checkmate simplifies writing unit tests using the framework "testthat" byextending it with plenty of additional expectation functions, and registered Croutines are available for package developers to perform assertions onarbitrary SEXPs (internal data structure for R objects implemented as struct inC) in compiled code.