Functions in Haskell
* haskell programming1. Defining Functions
Functions are defined simply and used simply. The function name is followed by parameters separated by spaces. But when defining functions, there’s a = and after that we define what the function does.(https://learnyouahaskell.github.io/starting-out.html#babys-first-functions)
doubleMe :: Int -> Int doubleMe x = x + x doubleMe 2
But what are the Int -> things?
Those are type declarators, and the :: is a type classifier. doubleMe takes an int and returns an Int. It would fail if we did something like
doubleMe :: Int -> Int doubleMe x = x + x doubleMe 9 9
or
doubleMe :: Int -> Int doubleMe x = x + x doubleMe 3.1
1.1. Example 1
Lets take a more complicated example. This is the decision-making system for Ethics(5). We start by doing a pattern match on the stimulus field inside the ctx (Input Context)
decide :: Context -> Action
decide ctx =
case stimulus ctx of
Ambiguous ->
if pressure ctx > 4
then WithdrawalExternal
else MinimalResponse
BoundaryViolation _ ->
WithdrawExternal
AidRequest _ ->
if aidAllowed ctx
then ProvideAid
else WithdrawInternal
Neutral ->
if pressure ctx > 7
then WithdrawInternal
else if minimalPositiveAllowed ctx
then MinimalPositive
else NoOp
If the stimulus is ambiguous and the pressure is above 4, then you will withdraw externally, else you will give a minimalresponse. AidRequest _ ->: AidRequest usually requires an agent, but here it doesnt matter which agent did it hence the wildcard _, we will always withdraw on boundary violation. Then on neutral stimuli we will check if minimalpositive is allowed.
1.2. Just, and Maybe
Maybe is the "wrapper" (the type). It is defined like this:
data Maybe a = Nothing | Just a
- a: This is a type variable (like Int, String, or your Agent type).
- Nothing: Represents a failed search, an empty field, or "no value."
- Just a: Represents success, containing the actual value.
2. Elsewhere
2.1. References
2.2. In my garden
Notes that link to this note (AKA backlinks).