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array: specialize S.takeWhile and S.dropWhile
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@davidchambers
davidchambers committed Apr 5, 2019
1 parent 5d82380 commit bc17e0d
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96 changes: 54 additions & 42 deletions index.js
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Expand Up @@ -1068,46 +1068,6 @@
impl: curry2 (Z.reject)
};

//# takeWhile :: Filterable f => (a -> Boolean) -> f a -> f a
//.
//. Curried version of [`Z.takeWhile`][]. Discards the first element which
//. does not satisfy the predicate, and all subsequent elements.
//.
//. See also [`dropWhile`](#dropWhile).
//.
//. ```javascript
//. > S.takeWhile (S.odd) ([3, 3, 3, 7, 6, 3, 5, 4])
//. [3, 3, 3, 7]
//.
//. > S.takeWhile (S.even) ([3, 3, 3, 7, 6, 3, 5, 4])
//. []
//. ```
_.takeWhile = {
consts: {f: [Z.Filterable]},
types: [$.Predicate (a), f (a), f (a)],
impl: curry2 (Z.takeWhile)
};

//# dropWhile :: Filterable f => (a -> Boolean) -> f a -> f a
//.
//. Curried version of [`Z.dropWhile`][]. Retains the first element which
//. does not satisfy the predicate, and all subsequent elements.
//.
//. See also [`takeWhile`](#takeWhile).
//.
//. ```javascript
//. > S.dropWhile (S.odd) ([3, 3, 3, 7, 6, 3, 5, 4])
//. [6, 3, 5, 4]
//.
//. > S.dropWhile (S.even) ([3, 3, 3, 7, 6, 3, 5, 4])
//. [3, 3, 3, 7, 6, 3, 5, 4]
//. ```
_.dropWhile = {
consts: {f: [Z.Filterable]},
types: [$.Predicate (a), f (a), f (a)],
impl: curry2 (Z.dropWhile)
};

//# map :: Functor f => (a -> b) -> f a -> f b
//.
//. Curried version of [`Z.map`][].
Expand Down Expand Up @@ -3246,6 +3206,33 @@
impl: takeLast
};

//# takeWhile :: (a -> Boolean) -> Array a -> Array a
//.
//. Discards the first element which does not satisfy the predicate,
//. and all subsequent elements.
//.
//. See also [`dropWhile`](#dropWhile).
//.
//. ```javascript
//. > S.takeWhile (S.odd) ([3, 3, 3, 7, 6, 3, 5, 4])
//. [3, 3, 3, 7]
//.
//. > S.takeWhile (S.even) ([3, 3, 3, 7, 6, 3, 5, 4])
//. []
//. ```
function takeWhile(pred) {
return function(xs) {
var idx = 0;
while (idx < xs.length && pred (xs[idx])) idx += 1;
return xs.slice (0, idx);
};
}
_.takeWhile = {
consts: {},
types: [$.Predicate (a), $.Array (a), $.Array (a)],
impl: takeWhile
};

//# drop :: Integer -> Array a -> Maybe (Array a)
//.
//. Returns Just all but the first N elements of the given array if N is
Expand Down Expand Up @@ -3301,6 +3288,33 @@
impl: dropLast
};

//# dropWhile :: (a -> Boolean) -> Array a -> Array a
//.
//. Retains the first element which does not satisfy the predicate,
//. and all subsequent elements.
//.
//. See also [`takeWhile`](#takeWhile).
//.
//. ```javascript
//. > S.dropWhile (S.odd) ([3, 3, 3, 7, 6, 3, 5, 4])
//. [6, 3, 5, 4]
//.
//. > S.dropWhile (S.even) ([3, 3, 3, 7, 6, 3, 5, 4])
//. [3, 3, 3, 7, 6, 3, 5, 4]
//. ```
function dropWhile(pred) {
return function(xs) {
var idx = 0;
while (idx < xs.length && pred (xs[idx])) idx += 1;
return xs.slice (idx);
};
}
_.dropWhile = {
consts: {},
types: [$.Predicate (a), $.Array (a), $.Array (a)],
impl: dropWhile
};

//# size :: Foldable f => f a -> Integer
//.
//. Returns the number of elements of the given structure.
Expand Down Expand Up @@ -5009,7 +5023,6 @@
//. [`Z.compose`]: v:sanctuary-js/sanctuary-type-classes#compose
//. [`Z.concat`]: v:sanctuary-js/sanctuary-type-classes#concat
//. [`Z.contramap`]: v:sanctuary-js/sanctuary-type-classes#contramap
//. [`Z.dropWhile`]: v:sanctuary-js/sanctuary-type-classes#dropWhile
//. [`Z.duplicate`]: v:sanctuary-js/sanctuary-type-classes#duplicate
//. [`Z.empty`]: v:sanctuary-js/sanctuary-type-classes#empty
//. [`Z.equals`]: v:sanctuary-js/sanctuary-type-classes#equals
Expand All @@ -5031,7 +5044,6 @@
//. [`Z.promap`]: v:sanctuary-js/sanctuary-type-classes#promap
//. [`Z.reject`]: v:sanctuary-js/sanctuary-type-classes#reject
//. [`Z.sequence`]: v:sanctuary-js/sanctuary-type-classes#sequence
//. [`Z.takeWhile`]: v:sanctuary-js/sanctuary-type-classes#takeWhile
//. [`Z.traverse`]: v:sanctuary-js/sanctuary-type-classes#traverse
//. [`Z.zero`]: v:sanctuary-js/sanctuary-type-classes#zero
//. [`show`]: v:sanctuary-js/sanctuary-show#show
Expand Down
6 changes: 1 addition & 5 deletions test/dropWhile.js
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Expand Up @@ -9,14 +9,10 @@ test ('dropWhile', () => {

eq (typeof S.dropWhile) ('function');
eq (S.dropWhile.length) (1);
eq (S.show (S.dropWhile)) ('dropWhile :: Filterable f => (a -> Boolean) -> f a -> f a');
eq (S.show (S.dropWhile)) ('dropWhile :: (a -> Boolean) -> Array a -> Array a');

eq (S.dropWhile (S.odd) ([3, 3, 3, 7, 6, 3, 5, 4])) ([6, 3, 5, 4]);
eq (S.dropWhile (S.even) ([3, 3, 3, 7, 6, 3, 5, 4])) ([3, 3, 3, 7, 6, 3, 5, 4]);
eq (S.dropWhile (S.odd) ([])) ([]);

eq (S.dropWhile (S.odd) (S.Just (1))) (S.Nothing);
eq (S.dropWhile (S.even) (S.Just (1))) (S.Just (1));
eq (S.dropWhile (S.odd) (S.Nothing)) (S.Nothing);

});
6 changes: 1 addition & 5 deletions test/takeWhile.js
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Original file line number Diff line number Diff line change
Expand Up @@ -9,14 +9,10 @@ test ('takeWhile', () => {

eq (typeof S.takeWhile) ('function');
eq (S.takeWhile.length) (1);
eq (S.show (S.takeWhile)) ('takeWhile :: Filterable f => (a -> Boolean) -> f a -> f a');
eq (S.show (S.takeWhile)) ('takeWhile :: (a -> Boolean) -> Array a -> Array a');

eq (S.takeWhile (S.odd) ([3, 3, 3, 7, 6, 3, 5, 4])) ([3, 3, 3, 7]);
eq (S.takeWhile (S.even) ([3, 3, 3, 7, 6, 3, 5, 4])) ([]);
eq (S.takeWhile (S.odd) ([])) ([]);

eq (S.takeWhile (S.odd) (S.Just (1))) (S.Just (1));
eq (S.takeWhile (S.even) (S.Just (1))) (S.Nothing);
eq (S.takeWhile (S.odd) (S.Nothing)) (S.Nothing);

});

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