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davidchambers/lens.mjs

Last active May 3, 2021 14:30
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Revisions

  1. davidchambers revised this gist Apr 27, 2021. 1 changed file with 1 addition and 8 deletions.
    9 changes: 1 addition & 8 deletions lens.mjs
    View file
    Original file line number Diff line number Diff line change
    @@ -2,21 +2,14 @@ import S from 'sanctuary';
    import Identity from 'sanctuary-identity';


    // Constant :: b -> Constant a b
    const Constant = x => ({
    '@@type': 'sanctuary-constant/Constant',
    'fantasy-land/map': f => Constant (x),
    'fantasy-land/extract': () => x,
    });

    // lens :: (s -> a) -> (a -> s -> s) -> Lens s a
    const lens = getter => setter => f => s => (
    S.map (v => setter (v) (s))
    (f (getter (s)))
    );

    // view :: Lens s a -> s -> a
    const view = l => x => S.extract (l (Constant) (x));
    const view = l => x => (l (S.Left) (x)).value;

    // over :: Lens s a -> (a -> a) -> s -> s
    const over = l => f => x => S.extract (l (y => Identity (f (y))) (x));
  2. davidchambers created this gist Apr 27, 2021.
    31 changes: 31 additions & 0 deletions lens.mjs
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,31 @@
    import S from 'sanctuary';
    import Identity from 'sanctuary-identity';


    // Constant :: b -> Constant a b
    const Constant = x => ({
    '@@type': 'sanctuary-constant/Constant',
    'fantasy-land/map': f => Constant (x),
    'fantasy-land/extract': () => x,
    });

    // lens :: (s -> a) -> (a -> s -> s) -> Lens s a
    const lens = getter => setter => f => s => (
    S.map (v => setter (v) (s))
    (f (getter (s)))
    );

    // view :: Lens s a -> s -> a
    const view = l => x => S.extract (l (Constant) (x));

    // over :: Lens s a -> (a -> a) -> s -> s
    const over = l => f => x => S.extract (l (y => Identity (f (y))) (x));

    // email :: Lens User String
    const email = lens (user => user.email) (email => user => ({...user, email}));

    // user :: User
    const user = {id: 1, email: '[email protected]'};

    console.log (view (email) (user));
    console.log (over (email) (S.toUpper) (user));