I think reduce takes two arguments: the growing seed and the current front.

You're trying to get (a[0]-b[0])^^2 + (a[1]-b[1])^^2 + ..., right?

Try this:

module euclid;

import std.stdio;

double euclid_dist( double[] pt1, double[] pt2 ) {

assert( pt1.length == pt2.length );

import std.algorithm;

import std.math;

import std.range;

return sqrt(0.0.reduce!( (sum,pair) => sum + (pair[0]-pair[1])^^2 )(zip(pt1, pt2)));

}

void main()

{

double[] arr1 = [0.0, 1.0, 0.1];

double[] arr2 = [1.0, -1.0, 0.0];

writeln(euclid_dist(arr1,arr2));

}

On Thu, Oct 31, 2013 at 8:12 PM, Craig Dillabaugh <cdillaba@cg.scs.carleton.ca> wrote:

I am trying to calculate the Euclidean Distance between two
points. I currently have the following function (that doesn't
compile):

double euclid_dist( double[] pt1, double[] pt2 ) {
assert( pt1.length == pt2.length );

return sqrt(
zip(pt1, pt2).reduce!(function(e) { return
(e[1]-e[0])*(e[1]-e[0]); })(0.0)
);
}

Hopefully it is clear what I am trying to do. I want zip to
create a range that is a tuple of the point's coordinate pairs,
and then use reduce to sum the squared differences. I get the
following error but can't figure out how to fix my syntax:

euclid.d(13): Error: template
euclid.euclid_dist.reduce!(__funcliteral2).reduce does not match
any function template declaration. Candidates are:
/usr/include/dmd/phobos/std/algorithm.d(688):
euclid.euclid_dist.reduce!(__funcliteral2).reduce(Args...)(Args
args) if (Args.length > 0 && Args.length <= 2 &&
isIterable!(Args[__dollar - 1]))
euclid.d(13): Error: template
euclid.euclid_dist.reduce!(__funcliteral2).reduce(Args...)(Args
args) if (Args.length > 0 && Args.length <= 2 &&
isIterable!(Args[__dollar - 1])) cannot deduce template function
from argument types !()(Zip!(double[], double[]), double)
Failed: 'dmd' '-v' '-o-' 'euclid.d' '-I.'

I know I could use a simple foreach loop with my zip command, or
even std.numeric.euclidean( ... ), but I am trying to be cute
here!

Cheers,
Craig