returning a list

[Jeff Thies]

I'd like to return two values from a function. I'm doing this:

function getTwo(){
// some code
return new Array(value_a,v alue_b);
}

var returnArray=get Two(some_var);

var value_a=returnA rray[0];
var value_b=returnA rray[1];

Is there a cleaner way of doing that? I'm used to perl list assignments.

Cheers,
Jeff

[Dr John Stockton]

Re: returning a list

JRS: In article <0sjEb.3675$wL6 .1982@newsread1 .news.atl.earth link.net>,
seen in news:comp.lang. javascript, Jeff Thies <nospam@nospam. net> posted
at Thu, 18 Dec 2003 15:10:52 :-[color=blue]
> I'd like to return two values from a function. I'm doing this:
>
>function getTwo(){
>// some code
>return new Array(value_a,v alue_b);
>}
>
>var returnArray=get Two(some_var);
>
>var value_a=returnA rray[0];
>var value_b=returnA rray[1];
>
> Is there a cleaner way of doing that? I'm used to perl list assignments.[/color]

Yes. You could have written return [value_a, value_b] } .

However, if the result is not naturally an array, consider

... return { A:value_a, B:value_b } }

then with (getTwo(some_va r)) { var value_a = A, value_b = B }

or Ob = getTwo(some_var )
and then work with Ob.A & Ob.B .

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 IE 4 ©
<URL:http://jibbering.com/faq/> Jim Ley's FAQ for news:comp.lang. javascript
<URL:http://www.merlyn.demo n.co.uk/js-index.htm> Jsc maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/> TP/BP/Delphi/Jsc/&c, FAQ topics, links.

[Jeff Thies]

Re: returning a list

> However, if the result is not naturally an array, consider[color=blue]
>
> ... return { A:value_a, B:value_b } }
>
> or Ob = getTwo(some_var )
> and then work with Ob.A & Ob.B .[/color]

That's really nice! I'm calling a function that calculates many different
properties. Now I can retrieve any of these that are in the hash. Perfect
for astronomical calculations.

BTW. Wanted to thank you for the javascript time/date FAQ. Used it a bunch
yesterday!

Cheers,
Jeff
[color=blue]
> --
> © John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 IE[/color]
4 ©[color=blue]
> <URL:http://jibbering.com/faq/> Jim Ley's FAQ for[/color]
news:comp.lang. javascript[color=blue]
> <URL:http://www.merlyn.demo n.co.uk/js-index.htm> Jsc maths, dates,[/color]
sources.[color=blue]
> <URL:http://www.merlyn.demo n.co.uk/> TP/BP/Delphi/Jsc/&c, FAQ topics,[/color]
links.

[Grant Wagner]

Re: returning a list

Jeff Thies wrote:
[color=blue][color=green]
> > However, if the result is not naturally an array, consider
> >
> > ... return { A:value_a, B:value_b } }
> >
> > or Ob = getTwo(some_var )
> > and then work with Ob.A & Ob.B .[/color]
>
> That's really nice! I'm calling a function that calculates many different
> properties. Now I can retrieve any of these that are in the hash. Perfect
> for astronomical calculations.
>
> BTW. Wanted to thank you for the javascript time/date FAQ. Used it a bunch
> yesterday!
>
> Cheers,
> Jeff[/color]

If you know what you want to return, such as the description of a star, I would
strongly urge you to create an object Star, then return an instance of that
object. I don't know the properties of a star, but the code would look something
like:

function Star(distance, brightness, temperature) {
this.distance = distance;
this.brightness = brightness;
this.temperatur e = temperature;

this.setDistanc e = function(d) {
if (d > 1000000000) {
return -1;
} else {
this.distance = d;
return this.distance;
}
}
this.getDistanc e = function() {
return this.distance + 'au';
}
this.getBrightn ess = function() {
return this.brightness ;
}
this.getTempera ture = function() {
return this.temperatur e;
}
}

Then in your function that returns information about a star, it could do
something like:

return new Star(1, 2, 3);

And the code that uses the returned value would be:

var someStar = someFunctionTha tReturnsAStarOb ject();
document.write( 'The star is ' + someStar.getDis tance() + ' away');
if (someStar.setDi stance(10000000 0000) == -1) {
document.write( 'Something went wrong setting the star\'s distance');
} else {
document.write( 'The star is now ' + someStar.getDis tance() + ' away');
}

By creating a Star object, you can encapsulate data validation (as in the method
setDistance() and you manipulate the output in a single place (as with adding
'au' to the value returned by getDistance()).

--
| Grant Wagner <gwagner@agrico reunited.com>

* Client-side Javascript and Netscape 4 DOM Reference available at:
*

http://devedge.netscape.com/library/manuals/2000/javascript/1.3/reference/frames.html

* Internet Explorer DOM Reference available at:
*

http://msdn.microsoft.com/workshop/author/dhtml/reference/dhtml_reference_entry.asp

* Netscape 6/7 DOM Reference available at:
* http://www.mozilla.org/docs/dom/domref/
* Tips for upgrading JavaScript for Netscape 7 / Mozilla
* http://www.mozilla.org/docs/web-deve...upgrade_2.html

[Jeff Thies]

Re: returning a list

> If you know what you want to return, such as the description of a star, I
would[color=blue]
> strongly urge you to create an object Star, then return an instance of[/color]
that[color=blue]
> object. I don't know the properties of a star, but the code would look[/color]
something[color=blue]
> like:
>
> function Star(distance, brightness, temperature) {
> this.distance = distance;
> this.brightness = brightness;
> this.temperatur e = temperature;
>
> this.setDistanc e = function(d) {
> if (d > 1000000000) {
> return -1;
> } else {
> this.distance = d;
> return this.distance;
> }
> }
> this.getDistanc e = function() {
> return this.distance + 'au';
> }
> this.getBrightn ess = function() {
> return this.brightness ;
> }
> this.getTempera ture = function() {
> return this.temperatur e;
> }
> }[/color]

I thought of making this more object oriented. Usually when I call the
function I need 2 or 3 of the return values. These values just kind of fall
out as the calculation proceeds. ie: var a may take 100% of the
calculations, var b may take 80%. var c 98%. The calculations are extensive
and I didn't want to redo them.

Perhaps a wrapper around the function that turns it into an object???

Below is the Moon function:

function getMoon(date){
var lo=64.975464;
var Po=349.383063;
var No=151.950429;
var i=5.145396;

var sun=(findSun(da te));
var LAMDAsun=sun.LA MDAsun;
var Msun=sun.M;
var D=dayDiff(date) ;
var l=(13.1763966*D )+lo;
l=setRange(l);
Mm=setRange(l - .1114041 * D - Po);
var N=setRange(No - .0529539 * D);
var C=l-LAMDAsun;
var Ev=1.2739 * Math.sin(degree (2*C - Mm));
var Ae=.1858 * Math.sin(degree (Msun));
var A3=.37 * Math.sin(degree (Msun));
var Mpm=Mm+Ev-Ae-A3;
var Ec=6.2886 * Math.sin(degree (Mpm));
var A4=.214 * Math.sin(degree (2* Mpm));
var lp=l+Ev+Ec-Ae+A4;
var V=.6583 * Math.sin(degree (lp-LAMDAsun)*2);
var lpp=lp+V;

var Np=N + (.16 * Math.sin(degree (LAMDAsun))); // test should be wrong

var y=Math.sin(degr ee(lpp-Np)) * Math.cos(degree (i));
var x=Math.cos(degr ee(lpp-Np));
var arctan=Math.ata n(y/x)*180/Math.PI;

// arctan amiguity test
if((y>0)&&(x<0) ){arctan=arctan +180};
if((y<0)&&(x<0) ){arctan=arctan +180};
if((y<0)&&(x>0) ){arctan=arctan +360};

var LAMDAm=arctan+N p;
var Bm=Math.asin(Ma th.sin(degree(l pp-Np))*Math.sin(d egree(i)))*180/Math.PI;
var equatorial=ecli pticToEquatoria l(LAMDAm,Bm);
var Dm=lpp-LAMDAsun; // Dm is the phase of the moon in degrees ~13
degrees/day
var F=(1-Math.cos(degree (Dm)))/2;

return{F:F,Dm:D m,alpha:equator ial.alpha,delta :equatorial.del ta,B:Bm,LAMDA:L A
MDAm};
}

whew... Where do you draw the line between procedural, functional, object
oriented and functional retrieve "hash objects"?

maybe I should have gone to school after OO code was invented. No one ever
asks me to write fortran.

Cheers,
Jeff


[color=blue]
>
> Then in your function that returns information about a star, it could do
> something like:
>
> return new Star(1, 2, 3);
>
> And the code that uses the returned value would be:
>
> var someStar = someFunctionTha tReturnsAStarOb ject();
> document.write( 'The star is ' + someStar.getDis tance() + ' away');
> if (someStar.setDi stance(10000000 0000) == -1) {
> document.write( 'Something went wrong setting the star\'s distance');
> } else {
> document.write( 'The star is now ' + someStar.getDis tance() + ' away');
> }
>
> By creating a Star object, you can encapsulate data validation (as in the[/color]
method[color=blue]
> setDistance() and you manipulate the output in a single place (as with[/color]
adding[color=blue]
> 'au' to the value returned by getDistance()).
>
> --
> | Grant Wagner <gwagner@agrico reunited.com>
>
> * Client-side Javascript and Netscape 4 DOM Reference available at:
> *
>[/color]

http://devedge.netscape.com/library/manuals/2000/javascript/1.3/reference/fr

ames.html[color=blue]
>
> * Internet Explorer DOM Reference available at:
> *
>[/color]

http://msdn.microsoft.com/workshop/author/dhtml/reference/dhtml_reference_en

try.asp[color=blue]
>
> * Netscape 6/7 DOM Reference available at:
> * http://www.mozilla.org/docs/dom/domref/
> * Tips for upgrading JavaScript for Netscape 7 / Mozilla
> * http://www.mozilla.org/docs/web-deve...upgrade_2.html
>
>[/color]