13

DEBUGGING

Programmers often find that they spend

more time debugging a program than

actually writing it. Good debugging skills

are invaluable. In this chapter, we’ll discuss

debugging in R.

13.1 Fundamental Principles of Debugging

Beware of bugs in the above code; I have only proved it correct,

not tried it.

—Donald Knuth, pioneer of computer science

Though debugging is an art rather than a science, it involves some fun-

damental principles. Here, we’ll look at some debugging best practices.

13.1.1 The Essence of Debugging: The Principle of Confirmation...........

As Pete Salzman and I said in our book on debugging,The Art of Debugging,

with GDB, DDD, and Eclipse(No Starch Press, 2008), the principle of confir-

mation is the essence of debugging.