grokking reduce

[Dave Aronson]

The name "reduce" gives a good clue to what it *does* (reduce an array to one value based on the whole thing).  However, to understand how it *works* is easier if you use Ruby's alternate name for it: inject.  It sort of "injects" the function between each consecutive pair of elements in the array.  At least, that's effectively what happens if you use something like simple addition.  So:

[1,2,3,4].reduce(function(prev,curr) { return prev + curr })

is equivalent to 1 + 2 + 3 + 4.  Unfortunately, this style doesn't make it quite so clear, but if you do something like:

add = function(prev,curr) { return prev + curr };

[1,2,3,4].reduce(add);

that makes it a bit clearer in the reduce call, just what you're doing.  (Especially if you declare add further away.)

-Dave

[Joshua Clanton]

That's a great point, Dave. "Inject" is much more descriptive of how it works. On the other hand, I think "reduce" is more descriptive of what it does. :-)

And I definitely endorse the idea of naming the callback functions to make them more explicit.

Joshua Clanton

[Hugo Estrada]

On Tuesday, May 7, 2013 8:44:04 AM UTC-4, Dave Aronson wrote:

this is probably the best explanation for reduce that I have read.