You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
129 lines
4.1 KiB
129 lines
4.1 KiB
/*
|
|
MIT License http://www.opensource.org/licenses/mit-license.php
|
|
Author Mikola Lysenko @mikolalysenko
|
|
*/
|
|
|
|
"use strict";
|
|
|
|
/* cspell:disable-next-line */
|
|
// Refactor: Peter Somogyvari @petermetz
|
|
|
|
/** @typedef {">=" | "<=" | "<" | ">" | "-" } BinarySearchPredicate */
|
|
/** @typedef {"GE" | "GT" | "LT" | "LE" | "EQ" } SearchPredicateSuffix */
|
|
|
|
/**
|
|
* Helper function for compiling binary search functions.
|
|
*
|
|
* The generated code uses a while loop to repeatedly divide the search interval
|
|
* in half until the desired element is found, or the search interval is empty.
|
|
*
|
|
* The following is an example of a generated function for calling `compileSearch("P", "c(x,y)<=0", true, ["y", "c"], false)`:
|
|
*
|
|
* ```js
|
|
* function P(a,l,h,y,c){var i=l-1;while(l<=h){var m=(l+h)>>>1,x=a[m];if(c(x,y)<=0){i=m;l=m+1}else{h=m-1}}return i};
|
|
* ```
|
|
* @param {string} funcName The name of the function to be compiled.
|
|
* @param {string} predicate The predicate / comparison operator to be used in the binary search.
|
|
* @param {boolean} reversed Whether the search should be reversed.
|
|
* @param {string[]} extraArgs Extra arguments to be passed to the function.
|
|
* @param {boolean=} earlyOut Whether the search should return as soon as a match is found.
|
|
* @returns {string} The compiled binary search function.
|
|
*/
|
|
const compileSearch = (funcName, predicate, reversed, extraArgs, earlyOut) => {
|
|
const code = [
|
|
"function ",
|
|
funcName,
|
|
"(a,l,h,",
|
|
extraArgs.join(","),
|
|
"){",
|
|
earlyOut ? "" : "var i=",
|
|
reversed ? "l-1" : "h+1",
|
|
";while(l<=h){var m=(l+h)>>>1,x=a[m]"
|
|
];
|
|
|
|
if (earlyOut) {
|
|
if (!predicate.includes("c")) {
|
|
code.push(";if(x===y){return m}else if(x<=y){");
|
|
} else {
|
|
code.push(";var p=c(x,y);if(p===0){return m}else if(p<=0){");
|
|
}
|
|
} else {
|
|
code.push(";if(", predicate, "){i=m;");
|
|
}
|
|
if (reversed) {
|
|
code.push("l=m+1}else{h=m-1}");
|
|
} else {
|
|
code.push("h=m-1}else{l=m+1}");
|
|
}
|
|
code.push("}");
|
|
if (earlyOut) {
|
|
code.push("return -1};");
|
|
} else {
|
|
code.push("return i};");
|
|
}
|
|
return code.join("");
|
|
};
|
|
|
|
/**
|
|
* This helper functions generate code for two binary search functions:
|
|
* A(): Performs a binary search on an array using the comparison operator specified.
|
|
* P(): Performs a binary search on an array using a _custom comparison function_
|
|
* `c(x,y)` **and** comparison operator specified by `predicate`.
|
|
* @param {BinarySearchPredicate} predicate The predicate / comparison operator to be used in the binary search.
|
|
* @param {boolean} reversed Whether the search should be reversed.
|
|
* @param {SearchPredicateSuffix} suffix The suffix to be used in the function name.
|
|
* @param {boolean=} earlyOut Whether the search should return as soon as a match is found.
|
|
* @returns {Function} The compiled binary search function.
|
|
*/
|
|
const compileBoundsSearch = (predicate, reversed, suffix, earlyOut) => {
|
|
const arg1 = compileSearch("A", `x${predicate}y`, reversed, ["y"], earlyOut);
|
|
|
|
const arg2 = compileSearch(
|
|
"P",
|
|
`c(x,y)${predicate}0`,
|
|
reversed,
|
|
["y", "c"],
|
|
earlyOut
|
|
);
|
|
|
|
const fnHeader = "function dispatchBinarySearch";
|
|
|
|
const fnBody =
|
|
// eslint-disable-next-line no-multi-str
|
|
"(a,y,c,l,h){\
|
|
if(typeof(c)==='function'){\
|
|
return P(a,(l===void 0)?0:l|0,(h===void 0)?a.length-1:h|0,y,c)\
|
|
}else{\
|
|
return A(a,(c===void 0)?0:c|0,(l===void 0)?a.length-1:l|0,y)\
|
|
}}\
|
|
return dispatchBinarySearch";
|
|
|
|
const fnArgList = [arg1, arg2, fnHeader, suffix, fnBody, suffix];
|
|
const fnSource = fnArgList.join("");
|
|
// eslint-disable-next-line no-new-func
|
|
const result = new Function(fnSource);
|
|
return result();
|
|
};
|
|
|
|
/**
|
|
* These functions are used to perform binary searches on arrays.
|
|
* @example
|
|
* ```js
|
|
* const { gt, le} = require("./binarySearchBounds");
|
|
* const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
|
|
*
|
|
* // Find the index of the first element greater than 5
|
|
* const index1 = gt(arr, 5); // index1 === 3
|
|
*
|
|
* // Find the index of the first element less than or equal to 5
|
|
* const index2 = le(arr, 5); // index2 === 4
|
|
* ```
|
|
*/
|
|
module.exports = {
|
|
ge: compileBoundsSearch(">=", false, "GE"),
|
|
gt: compileBoundsSearch(">", false, "GT"),
|
|
lt: compileBoundsSearch("<", true, "LT"),
|
|
le: compileBoundsSearch("<=", true, "LE"),
|
|
eq: compileBoundsSearch("-", true, "EQ", true)
|
|
};
|