indique/elm-bounded-nat/2.0.0

NOTE: the latest version is 13.0.0

Nat.Bound

Min

type Min minimum

Min minimum: At least minimum.

   ↓ minimum
⨯ [✓ ✓ ✓ ✓ ✓ ✓ ✓...

Any natural number:

Nat (Min Nat0)

A number, at least 5:

Nat (Min Nat5)

In

type In minimum maximum

In minimum maximum: Somewhere within a minimum & maximum.

   ↓ minimum   ↓ maximum
⨯ [✓ ✓ ✓ ✓ ✓ ✓ ✓] ⨯ ⨯ ⨯...

Note: maximum >= minimum for every existing Nat (In ...):

percent : Nat (In minimum Nat100)

→ minimum <= Nat100

Only

type alias Only n =
In n n

Just the exact number.

Only useful in function annotations.

byte : Arr (Only Nat8) Bit -> Byte

→ A given Arr must have exact 8 Bits.

repeat : Nat (Only n) -> element -> Arr (Only n)


repeat (Nat.In.n nat6) "ok"
--> Arr (Only Nat6)

→ repeating an element n times will give you a Arr of n elements.

→ Every In NatXYZ (NatXYZPlus a) is also a Only NatXYZ, but not the other way around

N

type N n is difference

The actual value is present in the type.

Looking at the type

nat0 :
    -- natural number
    Nat
        (N
            -- 0 is the exact value at compile time
            Nat0
            Is
            -- 0 as a difference is a - a
            (Difference a To a)
        )

It is also used to describe a difference between two values.

interval :
    { first : Nat (N first Is (Difference range To last))
    , last : Nat (Only last)
    }
    -> Interval

→ because range is 0 or positive, last must also be at least as high as first.

If you only want to ensure that it is within a minimum (& maximum), Min or In is the right choice! This is most of the time the better choice for calculations.

type Is

No special meaning.

N n Is difference
type Difference a to b

b - a.

Difference a To (Nat1Plus a)

would describe a difference of 1.

type To

No special meaning.

Difference a To b