slist alternatives and similar packages
Based on the "Data Structures" category.
Alternatively, view slist alternatives based on common mentions on social networks and blogs.
-
parameterized-utils
A set of utilities for using indexed types including containers, equality, and comparison. -
justified-containers
Standard containers, with keys that carry type-level proofs of their own presence.
CodeRabbit: AI Code Reviews for Developers

Do you think we are missing an alternative of slist or a related project?
README
slist
⚠️ 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.
Comparison
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) |
Potential usage cases
- When you ask the size of the list too frequently.
- When you need to convert to data structures that require to know the list size in advance for allocating an array of the elements. Example: Vector data structure.
- When you need to serialise lists.
- When you need to control the behaviour depending on the finiteness of the list.
- When you need a more efficient or safe implementation of some functions.
*Note that all licence references and agreements mentioned in the slist README section above
are relevant to that project's source code only.