[plt-scheme] what is fold-left?

From: Eli Barzilay (eli at barzilay.org)
Date: Wed Feb 11 22:23:58 EST 2009

On Feb 11, Mike Eggleston wrote:
> Morning,
> I'm looking at some code at
> <http://funcall.blogspot.com/2007/08/naive-bayesian-classifier.html>. This
> code by default will not run in DrScheme. The code is using (fold-left
> ...). Looking at the function it looks like a (map ...), but I don't
> (yet) know why I can't just use a 'map' instead of the 'fold-left'.
> Any ideas? What does this function do that 'map' doesn't and why
> should it be used?

It's similar to `map' except that you give it a function to accumulate
the results.  Think of it as a generic swiss-army-knife of list
functions.  In PLT, you have it available as `foldl'.

          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                  http://www.barzilay.org/                 Maze is Life!

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