# Undefined Results

> Returning results a contract never specifies for a given input, leaving callers with undefined behavior.

Record: `lexicon:undefined-results`
Kind: anti-pattern
Layer: [Contracts Core](https://banes-lab.com/records/layer/contracts-core.md)
Canonical: https://banes-lab.com/ontology/lexicon#lexicon-undefined-results

Listed in [Lexicon terms](https://banes-lab.com/api/records/lexicon.md), after [Strict Fragile Parsers](https://banes-lab.com/records/lexicon/strict-fragile-parsers.md) and before [Compatibility Policy](https://banes-lab.com/records/lexicon/compatibility-policy.md).

## Category

- [Contracts / Interfaces / Compatibility](https://banes-lab.com/records/lexicon-category/contracts-interfaces-compatibility.md)

## Negated by

- [Postconditions](https://banes-lab.com/records/architecture/postconditions.md)

## Linked from

- [Contracts / Interfaces / Compatibility](https://banes-lab.com/ontology/principles/architecture-category-contracts-interfaces-compatibility.md)