lib: implement compare, splitByAndCompare, and compareLists

This commit is contained in:
Jan Malakhovski 2017-12-07 21:26:30 +00:00
parent aeb32cf187
commit bccab965b9
3 changed files with 52 additions and 3 deletions

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@ -56,7 +56,7 @@ let
replaceStrings seq stringLength sub substring tail; replaceStrings seq stringLength sub substring tail;
inherit (trivial) id const concat or and boolToString mergeAttrs inherit (trivial) id const concat or and boolToString mergeAttrs
flip mapNullable inNixShell min max importJSON warn info flip mapNullable inNixShell min max importJSON warn info
nixpkgsVersion mod; nixpkgsVersion mod compare splitByAndCompare;
inherit (fixedPoints) fix fix' extends composeExtensions inherit (fixedPoints) fix fix' extends composeExtensions
makeExtensible makeExtensibleWithCustomName; makeExtensible makeExtensibleWithCustomName;
@ -71,8 +71,8 @@ let
inherit (lists) singleton foldr fold foldl foldl' imap0 imap1 inherit (lists) singleton foldr fold foldl foldl' imap0 imap1
concatMap flatten remove findSingle findFirst any all count concatMap flatten remove findSingle findFirst any all count
optional optionals toList range partition zipListsWith zipLists optional optionals toList range partition zipListsWith zipLists
reverseList listDfs toposort sort take drop sublist last init reverseList listDfs toposort sort compareLists take drop sublist
crossLists unique intersectLists subtractLists last init crossLists unique intersectLists subtractLists
mutuallyExclusive; mutuallyExclusive;
inherit (strings) concatStrings concatMapStrings concatImapStrings inherit (strings) concatStrings concatMapStrings concatImapStrings
intersperse concatStringsSep concatMapStringsSep intersperse concatStringsSep concatMapStringsSep

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@ -385,6 +385,30 @@ rec {
if len < 2 then list if len < 2 then list
else (sort strictLess pivot.left) ++ [ first ] ++ (sort strictLess pivot.right)); else (sort strictLess pivot.left) ++ [ first ] ++ (sort strictLess pivot.right));
/* Compare two lists element-by-element.
Example:
compareLists compare [] []
=> 0
compareLists compare [] [ "a" ]
=> -1
compareLists compare [ "a" ] []
=> 1
compareLists compare [ "a" "b" ] [ "a" "c" ]
=> 1
*/
compareLists = cmp: a: b:
if a == []
then if b == []
then 0
else -1
else if b == []
then 1
else let rel = cmp (head a) (head b); in
if rel == 0
then compareLists cmp (tail a) (tail b)
else rel;
/* Return the first (at most) N elements of a list. /* Return the first (at most) N elements of a list.
Example: Example:

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@ -81,6 +81,31 @@ rec {
*/ */
mod = base: int: base - (int * (builtins.div base int)); mod = base: int: base - (int * (builtins.div base int));
/* C-style comparisons
a < b => -1
a == b => 0
a > b => 1
*/
compare = a: b:
if a < b
then -1
else if a > b
then 1
else 0;
/* Split type into two subtypes by predicate `p`, assume
forall x y . x < y if p x == true && p y == false
compare elements of the same subtype with `yes` and `no`
comparisons respectively.
*/
splitByAndCompare = p: yes: no: a: b:
if p a
then if p b then yes a b else -1
else if p b then 1 else no a b;
/* Reads a JSON file. */ /* Reads a JSON file. */
importJSON = path: importJSON = path:
builtins.fromJSON (builtins.readFile path); builtins.fromJSON (builtins.readFile path);