⚠️ Caution: this is a very opinionated library. There is no intention to replace the standard list data type. We are aware of every design decision we made for this package, and we are taking responsibility for that design. If you find it inappropriate, please, consider to use another library instead, that would fulfil your requirements.
This package introduces sized list data type — Slist
. The data type
has the following shape:
data Slist a = Slist
{ sList :: [a]
, sSize :: Size
}
As you can see that along with the familiar list, it contains Size
field that
represents the size of the structure. Slists can be finite or infinite, and this
is expressed with Size
.
data Size
= Size Int
| Infinity
⚠️ Caution:
Int
is used for the size by design. We had to make some trade-offs to provide the better (as we think) interface for users. For more details on the choice, see the Haddock documentation for theSize
data type.
This representation of the list gives some additional advantages. Getting the
length of the list is the "free" operation (runs in O(1)
). This property
helps to improve the performance for a bunch of functions like take
, drop
,
at
, etc. But also it doesn't actually add any overhead on the existing
functions.
Also, this allows to write a number of safe functions like safeReverse
,
safeHead
, safeLast
, safeIsSuffixOf
, etc.
Check out the comparison table between lists and slists performance.
Function | list (finite) | list (infinite) | Slist (finite) | Slist (infinite) |
---|---|---|---|---|
length |
O(n) |
<_hangs_> | O(1) |
O(1) |
safeLast |
O(n) |
<_hangs_> | O(n) |
O(1) |
init |
O(n) |
<_works infinitely_> | O(n) |
O(1) |
take |
O(min i n) |
O(i) |
0 < i < n : O(i) ; otherwise: O(1) |
O(i) |
at |
O(min i n) (run-time exception) |
O(i) (run-time exception) |
0 < i < n : O(i) ; otherwise: O(1) |
O(i) |
safeStripPrefix |
O(m) |
O(m) (can hang) |
O(m) |
O(m) |