On Dec 11, 7:50 pm, [EMAIL PROTECTED] wrote:
> On Dec 11, 4:53 pm, "William James" <[EMAIL PROTECTED]> 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? ;-)
Haskell looks the best though:
norm v = map (/ (sqrt (sum (map (^2) v)))) v
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