bisecting-between

Produces a unique value that sorts between two other given values.

background

This module makes it easy to select a unique value between any two bisecting numbers, where there are always unique values between any two such numbers. Read more about bisecting numbers here.

This module is inspired by Dominic Tarr's between module. This module aims to offer an equivalent API with the same key property of being commutative (i.e. inserting between two items does not change the positions of nodes later in a created list).

between is great, but the length of the identifier in the case of consecutive appends and prepends is very expensive, growing linearly:

var n = between(between.lo, between.hi)
for (var i=0; i < 100; i++) {
  if (i % 10 === 0) {
    console.log(n)
  }
  n = between(n, between.hi)
}

V
zy
zzzs
zzzzzV
zzzzzzy
zzzzzzzzs
zzzzzzzzzzV
zzzzzzzzzzzy
zzzzzzzzzzzzzs
zzzzzzzzzzzzzzzV

bisecting-between optimizes for minimizing the growth of string length in the append and prepend cases, growing logarithmically:

0
A
K
U
e
o
y
18
1I
1S

This trade-off makes random insertions more growth expensive instead. In certain applications (like text editors), long appends and prepends are far more common.

example

> var between = require('bisecting-between')()

> between()
'0'

> between('A', 'B')
'A.0'

> between('A.0', between.hi)
A.1

> between('E.C', 'F')
'E.D'

api

var between = BisectingBetween(alphabet)

Returns a function (that generates values between two other values) across the given string alphabet (where alphabet.charAt(0) is the zero value, the next is 1, etc). If not provided, the alphabet is the string '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'.

between(lo, hi)

Returns a bisecting number that is between two other bisecting numbers that will always sort as between lo and hi.

between.lo, between.hi

Fixed values that symbolize the absolute lowest and highest, respectively.

install

With npm installed, run

$ npm install bisecting-between

license

ISC

hackergrrl/bisecting-between