Reduce and where

[FlorianRappl]

Two new functions should be handy in many scenarios: where and reduce. The latter is a nice addition to map, which transforms elements (providing a mapping from the source to the target). It will reduce the N elements to a single item.

The where function is essentially filter in JS (or Where in LINQ).

reduce will work with matrices and objects. It requires three arguments: a function, a start value, and an object to operate on.

new { a: 5, b: 9, c: 10 } | reduce(add, 0) // 0 + 5 + 9 + 10
[1, 3, 10] | reduce(subtract, 10) // 10 - 1 - 3 - 10

where will work with matrices and objects. It requires two arguments: a function and an object to operate on.

new { a: 5, b: 9, c: 10 } | where(x => x > 8) // new { b: 9, c: 10 }
[1, 3, 10] | where(greater(2)) // [3, 10]

Remark In v0.9 I will change greater, less, etc. to be actually like greater(x, y) == y > x. Right now (v0.8) it is greater(x, y) == x > y. There are some other functions that need to be reversed to be better for chaining, e.g., subtract, pow, or divide.