Where can we introduce partiality in functions
Note
A function that is not total, is partial. Yet again pertaining to Haskell, but is valid for other FP languages.
Where partiality can be introduced:
- Non-exhaustive pattern matching
- Missing conditions in guards
- Any pattern matching, basically
- Unspecified fields of records / structs / etc.
- Using bottom, e.g.
errorandundefinedin Haskell - Non-terminating loops
- Seg faults, and other low-level issues
Be careful when using wildcards, as adding new cases to types will lead to unexpected behaviour - prefer matching on all cases of a type instead when pattern matching. Same goes when using error for seemingly unreachable code, or "trusting" that functions from libraries are total.
