Loopfeil

Loopfeil is a term used in computer programming to describe faults in loop constructs that lead to incorrect or undesired iteration behavior. The term blends the English word loop with the Norwegian word feil, meaning fault, and is used in some Nordic programming communities to refer to errors that arise specifically from loops in code.

Common forms include infinite loops, where termination never occurs; off-by-one errors, where the loop boundary is miscalculated; and logical errors in which the loop runs more or fewer times than intended or produces incorrect results. Root causes include modifying the loop control variable inside the loop; incorrect increment or decrement steps; wrong bounds when iterating over arrays or collections; or complex conditions that fail to reflect the intended loop invariant.

Impact and detection: Loopfeil can cause high CPU usage, unresponsive programs, memory exhaustion, or incorrect outputs. They are often found through code reviews, unit tests that exercise boundary cases, runtime logging of iteration counts, and static analysis or linters. Debuggers and tracing can help by stepping through iterations and validating the loop's invariant.

Prevention and best practices: Write termination conditions that are easy to reason about; avoid changing the loop control variable inside the loop. Prefer for loops or foreach constructs with explicit bounds when possible; implement guard conditions to prevent excessive iterations; add assertions about invariants to catch violations during development.

See also:

- infinite loop

- off-by-one error

- loop invariant

- iteration safety