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39 lines
1.2 KiB
39 lines
1.2 KiB
var _curry3 = require('./internal/_curry3');
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/**
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* Returns the result of "setting" the portion of the given data structure
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* focused by the given lens to the result of applying the given function to
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* the focused value.
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*
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* @func
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* @memberOf R
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* @since v0.16.0
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* @category Object
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* @typedefn Lens s a = Functor f => (a -> f a) -> s -> f s
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* @sig Lens s a -> (a -> a) -> s -> s
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* @param {Lens} lens
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* @param {*} v
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* @param {*} x
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* @return {*}
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* @see R.prop, R.lensIndex, R.lensProp
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* @example
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*
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* var headLens = R.lensIndex(0);
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*
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* R.over(headLens, R.toUpper, ['foo', 'bar', 'baz']); //=> ['FOO', 'bar', 'baz']
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*/
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module.exports = (function() {
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// `Identity` is a functor that holds a single value, where `map` simply
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// transforms the held value with the provided function.
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var Identity = function(x) {
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return {value: x, map: function(f) { return Identity(f(x)); }};
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};
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return _curry3(function over(lens, f, x) {
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// The value returned by the getter function is first transformed with `f`,
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// then set as the value of an `Identity`. This is then mapped over with the
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// setter function of the lens.
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return lens(function(y) { return Identity(f(y)); })(x).value;
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});
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}());
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