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lib/lists: Update documentation comments for doc generation

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Updates documentation comments with extra information for nixdoc[1]
compatibility.

[1]: https://github.com/tazjin/nixdoc
This commit is contained in:
Vincent Ambo 2018-10-27 19:23:06 +02:00
parent 0560caa578
commit 65f50a9bb0
1 changed files with 136 additions and 48 deletions
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184
lib/lists.nix
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@ -1,4 +1,5 @@
# General list operations.
{ lib }:
with lib.trivial;
let
@ -8,21 +9,23 @@ rec {
inherit (builtins) head tail length isList elemAt concatLists filter elem genList;
/* Create a list consisting of a single element. `singleton x' is
sometimes more convenient with respect to indentation than `[x]'
/* Create a list consisting of a single element. `singleton x` is
sometimes more convenient with respect to indentation than `[x]`
when x spans multiple lines.
Type: singleton :: a -> [a]
Example:
singleton "foo"
=> [ "foo" ]
*/
singleton = x: [x];
/* “right fold” a binary function `op' between successive elements of
`list' with `nul' as the starting value, i.e.,
`foldr op nul [x_1 x_2 ... x_n] == op x_1 (op x_2 ... (op x_n nul))'.
Type:
foldr :: (a -> b -> b) -> b -> [a] -> b
/* “right fold” a binary function `op` between successive elements of
`list` with `nul' as the starting value, i.e.,
`foldr op nul [x_1 x_2 ... x_n] == op x_1 (op x_2 ... (op x_n nul))`.
Type: foldr :: (a -> b -> b) -> b -> [a] -> b
Example:
concat = foldr (a: b: a + b) "z"
@ -42,16 +45,15 @@ rec {
else op (elemAt list n) (fold' (n + 1));
in fold' 0;
/* `fold' is an alias of `foldr' for historic reasons */
/* `fold` is an alias of `foldr` for historic reasons */
# FIXME(Profpatsch): deprecate?
fold = foldr;
/* “left fold”, like `foldr', but from the left:
/* “left fold”, like `foldr`, but from the left:
`foldl op nul [x_1 x_2 ... x_n] == op (... (op (op nul x_1) x_2) ... x_n)`.
Type:
foldl :: (b -> a -> b) -> b -> [a] -> b
Type: foldl :: (b -> a -> b) -> b -> [a] -> b
Example:
lconcat = foldl (a: b: a + b) "z"
@ -70,16 +72,20 @@ rec {
else op (foldl' (n - 1)) (elemAt list n);
in foldl' (length list - 1);
/* Strict version of `foldl'.
/* Strict version of `foldl`.
The difference is that evaluation is forced upon access. Usually used
with small whole results (in contract with lazily-generated list or large
lists where only a part is consumed.)
Type: foldl' :: (b -> a -> b) -> b -> [a] -> b
*/
foldl' = builtins.foldl' or foldl;
/* Map with index starting from 0
Type: imap0 :: (int -> a -> b) -> [a] -> [b]
Example:
imap0 (i: v: "${v}-${toString i}") ["a" "b"]
=> [ "a-0" "b-1" ]
@ -88,6 +94,8 @@ rec {
/* Map with index starting from 1
Type: imap1 :: (int -> a -> b) -> [a] -> [b]
Example:
imap1 (i: v: "${v}-${toString i}") ["a" "b"]
=> [ "a-1" "b-2" ]
@ -96,6 +104,8 @@ rec {
/* Map and concatenate the result.
Type: concatMap :: (a -> [b]) -> [a] -> [b]
Example:
concatMap (x: [x] ++ ["z"]) ["a" "b"]
=> [ "a" "z" "b" "z" ]
@ -118,15 +128,21 @@ rec {
/* Remove elements equal to 'e' from a list. Useful for buildInputs.
Type: remove :: a -> [a] -> [a]
Example:
remove 3 [ 1 3 4 3 ]
=> [ 1 4 ]
*/
remove = e: filter (x: x != e);
remove =
# Element to remove from the list
e: filter (x: x != e);
/* Find the sole element in the list matching the specified
predicate, returns `default' if no such element exists, or
`multiple' if there are multiple matching elements.
predicate, returns `default` if no such element exists, or
`multiple` if there are multiple matching elements.
Type: findSingle :: (a -> bool) -> a -> a -> [a] -> a
Example:
findSingle (x: x == 3) "none" "multiple" [ 1 3 3 ]
@ -136,14 +152,24 @@ rec {
findSingle (x: x == 3) "none" "multiple" [ 1 9 ]
=> "none"
*/
findSingle = pred: default: multiple: list:
findSingle =
# Predicate
pred:
# Default value to return if element was not found.
default:
# Default value to return if more than one element was found
multiple:
# Input list
list:
let found = filter pred list; len = length found;
in if len == 0 then default
else if len != 1 then multiple
else head found;
/* Find the first element in the list matching the specified
predicate or returns `default' if no such element exists.
predicate or return `default` if no such element exists.
Type: findFirst :: (a -> bool) -> a -> [a] -> a
Example:
findFirst (x: x > 3) 7 [ 1 6 4 ]
@ -151,12 +177,20 @@ rec {
findFirst (x: x > 9) 7 [ 1 6 4 ]
=> 7
*/
findFirst = pred: default: list:
findFirst =
# Predicate
pred:
# Default value to return
default:
# Input list
list:
let found = filter pred list;
in if found == [] then default else head found;
/* Return true iff function `pred' returns true for at least element
of `list'.
/* Return true if function `pred` returns true for at least one
element of `list`.
Type: any :: (a -> bool) -> [a] -> bool
Example:
any isString [ 1 "a" { } ]
@ -166,8 +200,10 @@ rec {
*/
any = builtins.any or (pred: foldr (x: y: if pred x then true else y) false);
/* Return true iff function `pred' returns true for all elements of
`list'.
/* Return true if function `pred` returns true for all elements of
`list`.
Type: all :: (a -> bool) -> [a] -> bool
Example:
all (x: x < 3) [ 1 2 ]
@ -177,19 +213,25 @@ rec {
*/
all = builtins.all or (pred: foldr (x: y: if pred x then y else false) true);
/* Count how many times function `pred' returns true for the elements
of `list'.
/* Count how many elements of `list` match the supplied predicate
function.
Type: count :: (a -> bool) -> [a] -> int
Example:
count (x: x == 3) [ 3 2 3 4 6 ]
=> 2
*/
count = pred: foldl' (c: x: if pred x then c + 1 else c) 0;
count =
# Predicate
pred: foldl' (c: x: if pred x then c + 1 else c) 0;
/* Return a singleton list or an empty list, depending on a boolean
value. Useful when building lists with optional elements
(e.g. `++ optional (system == "i686-linux") flashplayer').
Type: optional :: bool -> a -> [a]
Example:
optional true "foo"
=> [ "foo" ]
@ -200,13 +242,19 @@ rec {
/* Return a list or an empty list, depending on a boolean value.
Type: optionals :: bool -> [a] -> [a]
Example:
optionals true [ 2 3 ]
=> [ 2 3 ]
optionals false [ 2 3 ]
=> [ ]
*/
optionals = cond: elems: if cond then elems else [];
optionals =
# Condition
cond:
# List to return if condition is true
elems: if cond then elems else [];
/* If argument is a list, return it; else, wrap it in a singleton
@ -223,20 +271,28 @@ rec {
/* Return a list of integers from `first' up to and including `last'.
Type: range :: int -> int -> [int]
Example:
range 2 4
=> [ 2 3 4 ]
range 3 2
=> [ ]
*/
range = first: last:
range =
# First integer in the range
first:
# Last integer in the range
last:
if first > last then
[]
else
genList (n: first + n) (last - first + 1);
/* Splits the elements of a list in two lists, `right' and
`wrong', depending on the evaluation of a predicate.
/* Splits the elements of a list in two lists, `right` and
`wrong`, depending on the evaluation of a predicate.
Type: (a -> bool) -> [a] -> { right :: [a], wrong :: [a] }
Example:
partition (x: x > 2) [ 5 1 2 3 4 ]
@ -252,7 +308,7 @@ rec {
/* Splits the elements of a list into many lists, using the return value of a predicate.
Predicate should return a string which becomes keys of attrset `groupBy' returns.
`groupBy'' allows to customise the combining function and initial value
`groupBy'` allows to customise the combining function and initial value
Example:
groupBy (x: boolToString (x > 2)) [ 5 1 2 3 4 ]
@ -268,10 +324,6 @@ rec {
xfce = [ { name = "xfce"; script = "xfce4-session &"; } ];
}
groupBy' allows to customise the combining function and initial value
Example:
groupBy' builtins.add 0 (x: boolToString (x > 2)) [ 5 1 2 3 4 ]
=> { true = 12; false = 3; }
*/
@ -289,17 +341,27 @@ rec {
the merging stops at the shortest. How both lists are merged is defined
by the first argument.
Type: zipListsWith :: (a -> b -> c) -> [a] -> [b] -> [c]
Example:
zipListsWith (a: b: a + b) ["h" "l"] ["e" "o"]
=> ["he" "lo"]
*/
zipListsWith = f: fst: snd:
zipListsWith =
# Function to zip elements of both lists
f:
# First list
fst:
# Second list
snd:
genList
(n: f (elemAt fst n) (elemAt snd n)) (min (length fst) (length snd));
/* Merges two lists of the same size together. If the sizes aren't the same
the merging stops at the shortest.
Type: zipLists :: [a] -> [b] -> [{ fst :: a, snd :: b}]
Example:
zipLists [ 1 2 ] [ "a" "b" ]
=> [ { fst = 1; snd = "a"; } { fst = 2; snd = "b"; } ]
@ -308,6 +370,8 @@ rec {
/* Reverse the order of the elements of a list.
Type: reverseList :: [a] -> [a]
Example:
reverseList [ "b" "o" "j" ]
@ -321,8 +385,7 @@ rec {
`before a b == true` means that `b` depends on `a` (there's an
edge from `b` to `a`).
Examples:
Example:
listDfs true hasPrefix [ "/home/user" "other" "/" "/home" ]
== { minimal = "/"; # minimal element
visited = [ "/home/user" ]; # seen elements (in reverse order)
@ -336,7 +399,6 @@ rec {
rest = [ "/home" "other" ]; # everything else
*/
listDfs = stopOnCycles: before: list:
let
dfs' = us: visited: rest:
@ -361,7 +423,7 @@ rec {
`before a b == true` means that `b` should be after `a`
in the result.
Examples:
Example:
toposort hasPrefix [ "/home/user" "other" "/" "/home" ]
== { result = [ "/" "/home" "/home/user" "other" ]; }
@ -376,7 +438,6 @@ rec {
toposort (a: b: a < b) [ 3 2 1 ] == { result = [ 1 2 3 ]; }
*/
toposort = before: list:
let
dfsthis = listDfs true before list;
@ -467,26 +528,38 @@ rec {
/* Return the first (at most) N elements of a list.
Type: take :: int -> [a] -> [a]
Example:
take 2 [ "a" "b" "c" "d" ]
=> [ "a" "b" ]
take 2 [ ]
=> [ ]
*/
take = count: sublist 0 count;
take =
# Number of elements to take
count: sublist 0 count;
/* Remove the first (at most) N elements of a list.
Type: drop :: int -> [a] -> [a]
Example:
drop 2 [ "a" "b" "c" "d" ]
=> [ "c" "d" ]
drop 2 [ ]
=> [ ]
*/
drop = count: list: sublist count (length list) list;
drop =
# Number of elements to drop
count:
# Input list
list: sublist count (length list) list;
/* Return a list consisting of at most ‘count’ elements of ‘list’,
starting at index ‘start’.
/* Return a list consisting of at most `count` elements of `list`,
starting at index `start`.
Type: sublist :: int -> int -> [a] -> [a]
Example:
sublist 1 3 [ "a" "b" "c" "d" "e" ]
@ -494,7 +567,13 @@ rec {
sublist 1 3 [ ]
=> [ ]
*/
sublist = start: count: list:
sublist =
# Index at which to start the sublist
start:
# Number of elements to take
count:
# Input list
list:
let len = length list; in
genList
(n: elemAt list (n + start))
@ -504,6 +583,10 @@ rec {
/* Return the last element of a list.
This function throws an error if the list is empty.
Type: last :: [a] -> a
Example:
last [ 1 2 3 ]
=> 3
@ -512,7 +595,11 @@ rec {
assert lib.assertMsg (list != []) "lists.last: list must not be empty!";
elemAt list (length list - 1);
/* Return all elements but the last
/* Return all elements but the last.
This function throws an error if the list is empty.
Type: init :: [a] -> [a]
Example:
init [ 1 2 3 ]
@ -523,7 +610,7 @@ rec {
take (length list - 1) list;
/* return the image of the cross product of some lists by a function
/* Return the image of the cross product of some lists by a function.
Example:
crossLists (x:y: "${toString x}${toString y}") [[1 2] [3 4]]
@ -534,8 +621,9 @@ rec {
/* Remove duplicate elements from the list. O(n^2) complexity.
Example:
Type: unique :: [a] -> [a]
Example:
unique [ 3 2 3 4 ]
=> [ 3 2 4 ]
*/