loop invariant

"A note on a standard strategy for developing loop invariants and loops."

The Eiffel programming language provides native support for loop invariants.

In addition, the language supports a "check instruction" (a kind of "assert") and loop invariants.

Loop invariants are used to monitor specific properties of a loop during successive iterations.

Loop variants and loop invariants are used to express correctness of loops.

Loop invariants are essentially constants within a loop, but their value may change outside of the loop.

Hence, loop invariants and variants are provided by human users, or are inferred by some abstract interpretation procedure.

Furthermore, extended static checking aims to report errors by exploiting user-supplied specifications, in the form of pre- and post-conditions, loop invariants and class invariants.