Ideas worth adopting anywhere.
WHAT A PURE FUNCTION IS
One depending only on its inputs, with no side effects.
WHY THAT MATTERS
It is trivially testable, safely parallelisable, and easy to reason about.
WHAT IMMUTABILITY MEANS
Values that do not change after creation.
WHAT IT PREVENTS
An entire class of bugs where something changed unexpectedly.
WHY IT MATTERS FOR CONCURRENCY
Values that cannot change cannot be raced on.
WHAT FIRST-CLASS FUNCTIONS ENABLE
Passing behaviour as an argument.
WHAT THE STANDARD TRANSFORMATIONS ARE
- Mapping: transforming each element
- Filtering: selecting elements
- Reducing: combining elements into one result
WHY THOSE ARE PREFERABLE TO LOOPS
They state intent rather than mechanics, and they eliminate index errors.
WHAT COMPOSITION MEANS
Building complex behaviour from simple functions.
WHAT TO ADOPT REGARDLESS OF LANGUAGE
Minimising changing shared state Preferring pure functions where practical Using the standard transformations
WHAT NOT TO DO
Force a functional style where the language fights it.
WHAT MATTERS MORE THAN PURITY
Clarity.
