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Thu Dec 11 09:50:18 EST 2008

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On Dec 11, 4:53 pm, "William James" <w_a_x_... at yahoo.com> wrote:
> William James wrote:
> > John W Kennedy wrote:
>
> > > Xah Lee wrote:
> > > > In lisp, python, perl, etc, you'll have 10 or so lines. In C or
> > > > Java, you'll have 50 or hundreds lines.
>
> > > Java:
>
> > > static float[] normal(final float[] x) {
> > >    float sum = 0.0f;
> > >    for (int i = 0; i < x.length; ++i) sum += x[i] * x[i];
> > >    final float divisor = (float) Math.sqrt(sum);
> > >    float[] a = new float[x.length];
> > >    for (int i = 0; i < x.length; ++i) a[i] = x[i]/divisor;
> > >    return a;
> > > }
>
> > "We don't need no stinkin' loops!"
>
> > SpiderMonkey Javascript:
>
> > function normal( ary )
> > { div=Math.sqrt(ary.map(function(x) x*x).reduce(function(a,b) a+b))
> >   return ary.map(function(x) x/div)
> > }
>
> The variable "div" shouldn't be global.
>
> function normal( ary )
> { var div = Math.sqrt(
>     ary.map(function(x) x*x).reduce(function(a,b) a+b) )
>   return ary.map(function(x) x/div)
>
> }
>
>

Chicken Scheme:

(require 'srfi-1)
(define (norm vec)
  (map (cute / <> (sqrt (reduce + 0 (map (cute expt <> 2) vec))))
vec))

Cute huh? ;-)

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