| 1 | // //////////////////////////////
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| 2 | // ## class fuzzyFactory
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| 3 | // This class acts as a factory for objects. We can search for an object with approximately
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| 4 | // the desired properties (say a rectangle with width 2 and height 1)
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| 5 | // The lookupOrCreate() method looks for an existing object (for example it may find an existing rectangle
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| 6 | // with width 2.0001 and height 0.999. If no object is found, the user supplied callback is
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| 7 | // called, which should generate a new object. The new object is inserted into the database
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| 8 | // so it can be found by future lookupOrCreate() calls.
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| 9 | // Constructor:
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| 10 | // numdimensions: the number of parameters for each object
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| 11 | // for example for a 2D rectangle this would be 2
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| 12 | // tolerance: The maximum difference for each parameter allowed to be considered a match
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| 13 | const FuzzyFactory = function (numdimensions, tolerance) {
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| 14 | this.lookuptable = {}
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| 15 | this.multiplier = 1.0 / tolerance
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| 16 | }
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| 17 |
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| 18 | FuzzyFactory.prototype = {
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| 19 | // let obj = f.lookupOrCreate([el1, el2, el3], function(elements) {/* create the new object */});
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| 20 | // Performs a fuzzy lookup of the object with the specified elements.
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| 21 | // If found, returns the existing object
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| 22 | // If not found, calls the supplied callback function which should create a new object with
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| 23 | // the specified properties. This object is inserted in the lookup database.
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| 24 | lookupOrCreate: function (els, creatorCallback) {
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| 25 | let hash = ''
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| 26 | let multiplier = this.multiplier
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| 27 | els.forEach(function (el) {
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| 28 | let valueQuantized = Math.round(el * multiplier)
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| 29 | hash += valueQuantized + '/'
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| 30 | })
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| 31 | if (hash in this.lookuptable) {
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| 32 | return this.lookuptable[hash]
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| 33 | } else {
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| 34 | let object = creatorCallback(els)
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| 35 | let hashparts = els.map(function (el) {
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| 36 | let q0 = Math.floor(el * multiplier)
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| 37 | let q1 = q0 + 1
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| 38 | return ['' + q0 + '/', '' + q1 + '/']
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| 39 | })
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| 40 | let numelements = els.length
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| 41 | let numhashes = 1 << numelements
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| 42 | for (let hashmask = 0; hashmask < numhashes; ++hashmask) {
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| 43 | let hashmaskShifted = hashmask
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| 44 | hash = ''
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| 45 | hashparts.forEach(function (hashpart) {
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| 46 | hash += hashpart[hashmaskShifted & 1]
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| 47 | hashmaskShifted >>= 1
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| 48 | })
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| 49 | this.lookuptable[hash] = object
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| 50 | }
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| 51 | return object
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| 52 | }
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| 53 | }
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| 54 | }
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| 55 |
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| 56 | module.exports = FuzzyFactory
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