Feature Request: findGreatestLessThan, findLeastGreaterThan

[tijszwinkels]

Thank you for this great project! - I'm using SortedSet to store measurements in order of timestamp. For this use-case, it would be immensely useful to get the values that are closest to (just above, or just below) a measurements.

This could be done by implementing the following methods:

• findGreatestLessThan
• findLeastGreaterThan
• findAllLessThan
• findAllGreaterThan

[applitopia]

Thank you for your suggestion. Searching sorted collections is an important feature, so we have just implemented the method from() that allows efficiently search collections like SortedSet and SortedMap.

Searching SortedSet

Many real applications require ability to efficiently search in a sorted dataset. The method:

from(value, backwards) 

returns a sequence that represents a subset of a sorted set starting with value up to the last element in the set.

If the optional parameter backwards is set to true, the returned sequence will list the entries backwards, starting with value down to the first element in the set.

Example:

const { SortedSet } = require('immutable-sorted');

const abc = SortedSet(["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]);

> abc.from("R");
Seq { "R", "S", "T", "U", "V", "W", "X", "Y", "Z" }

> abc.from("R", true);
Seq { "R", "Q", "P", "O", "N", "M", "L", "K", "J", "I", "H", "G", "F", "E", "D", "C", "B", "A" }

The method from() can be efficiently combined with take() to retrieve the desired number of values or with takeWhile() to retrieve a specific range:

> abc.from("R").take(5);
Seq { "R", "S", "T", "U", "V" }

> abc.from("R").takeWhile(s => s < "W");
Seq { "R", "S", "T", "U", "V" }

> abc.from("R", true).take(5);
Seq { "R", "Q", "P", "O", "N" }

> abc.from("R", true).takeWhile(s => s > "K");
Seq { "R", "Q", "P", "O", "N", "M", "L" }

Searching SortedMap

Many real applications require ability to efficiently search in a sorted data structure. The method:

from(key, backwards)

returns a sequence that represents a portion of this sorted map starting with a specific key up to the last entry in the sorted map.

If the optional parameter backwards is set to true, the returned sequence will list the entries backwards, starting with key down to the first entry in the sorted map.

Example:

> const abc = SortedMap([["A", "a"], ["B", "b"], ["C", "c"], ["D", "d"], ["E", "e"], ["F", "f"], ["G", "g"], ["H", "h"], ["I", "i"], ["J", "j"], ["K", "k"], ["L", "l"], ["M", "m"], ["N", "n"], ["O", "o"], ["P", "p"], ["Q", "q"], ["R", "r"], ["S", "s"], ["T", "t"], ["U", "u"], ["V", "v"], ["W", "w"], ["X", "x"], ["Y", "y"], ["Z", "z"]]);

> abc.from("R");
Seq { "R": "r", "S": "s", "T": "t", "U": "u", "V": "v", "W": "w", "X": "x", "Y": "y", "Z": "z" }

> abc.from("R", true);
Seq { "R": "r", "Q": "q", "P": "p", "O": "o", "N": "n", "M": "m", "L": "l", "K": "k", "J": "j", "I": "i", "H": "h", "G": "g", "F": "f", "E": "e", "D": "d", "C": "c", "B": "b", "A": "a" }

The method from() can be efficiently combined with take() to retrieve the desired number of values or with takeWhile() to retrieve a specific range:

> abc.from("R").take(5);
Seq { "R": "r", "S": "s", "T": "t", "U": "u", "V": "v" }

> abc.from("R").takeWhile((v, k) => k < "W");
Seq { "R": "r", "S": "s", "T": "t", "U": "u", "V": "v" }

> abc.from("R", true).take(5);
Seq { "R": "r", "Q": "q", "P": "p", "O": "o", "N": "n" }

> abc.from("R", true).takeWhile((v, k) => k > "K");
Seq { "R": "r", "Q": "q", "P": "p", "O": "o", "N": "n", "M": "m", "L": "l" }

[tijszwinkels]

awesome, thank you! 👍