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Replace mergeSort with Array.prototype.sort #355

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Replace mergeSort with Array.prototype.sort #355

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54 changes: 28 additions & 26 deletions lib/scope.js
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Expand Up @@ -46,7 +46,6 @@
import {
defaults,
keep_name,
mergeSort,
push_uniq,
make_node,
return_false,
Expand Down Expand Up @@ -918,35 +917,29 @@ AST_Toplevel.DEFMETHOD("compute_char_frequency", function(options) {
}
});

const base54 = (() => {
const leading = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ$_".split("");
const digits = "0123456789".split("");
let chars;
let frequency;
function reset() {
frequency = new Map();
leading.forEach(function(ch) {
frequency.set(ch, 0);
});
digits.forEach(function(ch) {
frequency.set(ch, 0);
});
}
base54.consider = function(str, delta) {
for (var i = str.length; --i >= 0;) {
const base54 = (function() {
const freq = new Map();

const digits = init("0123456789");
const leading = init("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ$_");
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sort method only used for two arrays above which have 10 and 54 elements

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It looks like the threshold between insert sort (stable) and quick sort (unstable) is 10 elements. So digits would always use insertion sort, but leading wouldn't. 😕

let chars, frequency = new Map(freq);

base54.consider = (str, delta) => {
for (let i = str.length; --i >= 0;) {
frequency.set(str[i], frequency.get(str[i]) + delta);
}
};
function compare(a, b) {
return frequency.get(b) - frequency.get(a);
}
base54.sort = function() {
chars = mergeSort(leading, compare).concat(mergeSort(digits, compare));
base54.sort = () => {
chars = leading.sort(compare).concat(digits.sort(compare));
};
base54.reset = reset;
reset();
base54.reset = () => {
frequency = new Map(freq);
};

return base54;

function base54(num) {
var ret = "", base = 54;
let ret = "", base = 54;
num++;
do {
num--;
Expand All @@ -956,7 +949,16 @@ const base54 = (() => {
} while (num > 0);
return ret;
}
return base54;

function init(chars) {
const array = chars.split("");
array.forEach((ch, i) => freq.set(ch, -1e-2 * i));
return array;
}

function compare(a, b) {
return frequency.get(b) - frequency.get(a);
}
})();

export {
Expand Down
25 changes: 0 additions & 25 deletions lib/utils/index.js
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Expand Up @@ -169,30 +169,6 @@ function remove(array, el) {
}
}

function mergeSort(array, cmp) {
if (array.length < 2) return array.slice();
function merge(a, b) {
var r = [], ai = 0, bi = 0, i = 0;
while (ai < a.length && bi < b.length) {
cmp(a[ai], b[bi]) <= 0
? r[i++] = a[ai++]
: r[i++] = b[bi++];
}
if (ai < a.length) r.push.apply(r, a.slice(ai));
if (bi < b.length) r.push.apply(r, b.slice(bi));
return r;
}
function _ms(a) {
if (a.length <= 1)
return a;
var m = Math.floor(a.length / 2), left = a.slice(0, m), right = a.slice(m);
left = _ms(left);
right = _ms(right);
return merge(left, right);
}
return _ms(array);
}

function makePredicate(words) {
if (!Array.isArray(words)) words = words.split(" ");

Expand Down Expand Up @@ -286,7 +262,6 @@ export {
map_to_object,
MAP,
member,
mergeSort,
noop,
push_uniq,
regexp_source_fix,
Expand Down