function and arguments as aguments

**UnaCoder** · Feb 15 '06, 08:55 PM

Re: function and arguments as aguments

You would be better off designing Sum to take an array as an argument,
then you can just pass the array of arguments to Sum

**Telmo Costa** · Feb 15 '06, 09:25 PM

Re: function and arguments as aguments

UnaCoder wrote:[color=blue]
> You would be better off designing Sum to take an array as an argument,
> then you can just pass the array of arguments to Sum
>[/color]

I was looking for a generic solution. But I presume for your replay that
there is no direct solution (at least no direct solution known by you
;) ).

**UnaCoder** · Feb 15 '06, 10:15 PM

Re: function and arguments as aguments

Well I thought there was and I researched java script to see if you can
invoke a string containing java script code. the solution that seemed
intuitive would be to do something like:

function Tunnel() {
function_name= arguments[0];
arguments.shift (); args = arguments.join( );
eval function_name + "(" + args + ");";
}

I didn't put any error checking in there, or test that code, but as far
as I know that should work =)

**Michael Winter** · Feb 15 '06, 10:25 PM

Re: function and arguments as aguments

On 15/02/2006 17:42, Telmo Costa wrote:

[snip]
[color=blue]
> // calling Sum directly
> Sum(1,2,3,4);
>
> // calling Sum through Tunnel
> Tunnel(Sum, 1,2,3,4);
> --------------------------------------
>
> How should the Tunnel function be defined, knowing that the number of
> parameters passed are unknown?[/color]

The previous suggestion - rewrite the Sum function to take an array
argument - is preferable as it's the simplest and most compatible
solution. However, there is an alternative: the Function.protot ype.apply
method.

function tunnel(func) {
return func.apply(null ,
Array.prototype .slice.call(arg uments, 1));
}
function sum() {
var total = 0,
i = arguments.lengt h;

while (i--) {
total += arguments[i];
}
return total;
}

alert(tunnel(su m, 1, 2, 3, 4)); /* 10 */

The problem with this approach is that not all browsers, especially IE
with a pre-5.5 JScript library, do not implement either the
Function.protot ype.apply or call methods. Though both can be emulated,
it requires quite a significant (though relatively trivial) amount of
work to accommodate a general case.

Mike

--
Michael Winter
Prefix subject with [News] before replying by e-mail.

**Telmo Costa** · Feb 16 '06, 12:55 AM

Re: function and arguments as aguments

UnaCoder wrote:[color=blue]
> Well I thought there was and I researched java script to see if you can
> invoke a string containing java script code. the solution that seemed
> intuitive would be to do something like:
>
> function Tunnel() {
> function_name= arguments[0];
> arguments.shift (); args = arguments.join( );
> eval function_name + "(" + args + ");";
> }
>
> I didn't put any error checking in there, or test that code, but as far
> as I know that should work =)
>[/color]

I always think of eval function as cheating :) Michael's solution is
more what i was looking for.

To be honest, the function i'm working with only takes 1 argument, so it
is like using the array solution. I was just wondering.

Nevertheless, thank you both.

**RobG** · Feb 16 '06, 02:25 AM

Re: function and arguments as aguments

UnaCoder wrote:[color=blue]
> Well I thought there was and I researched java script to see if you can
> invoke a string containing java script code. the solution that seemed
> intuitive would be to do something like:
>
> function Tunnel() {
> function_name= arguments[0];
> arguments.shift (); args = arguments.join( );
> eval function_name + "(" + args + ");";
> }
>
> I didn't put any error checking in there, or test that code, but as far
> as I know that should work =)[/color]

Arguments is not an array, it's just a list with a few other properties
that make it look a bit like an array. Consequently, it doesn't have
split() or join() methods (and I don't think you can add them to its
prototype).

--
Rob

**RobG** · Feb 16 '06, 02:35 AM

Re: function and arguments as aguments

Telmo Costa wrote:[color=blue]
> Hi. I have the following code:
>
> --------------------------------------
> function Tunnel() {
> //arguments[0](???);
> }
>
> function Sum() {
> var sum = 0;
> for (i=0; i<arguments.len gth; i++) sum += arguments[i];
> alert(sum);
> };
>
> // calling Sum directly
> Sum(1,2,3,4);
>
> // calling Sum through Tunnel
> Tunnel(Sum, 1,2,3,4);
> --------------------------------------
>
> How should the Tunnel function be defined, knowing that the number of
> parameters passed are unknown?[/color]

How about:

function tunnel()
{
this.sum = function(x){
var s=x[0], i=x.length;
while (--i) s += x[i];
return s;
}
this.product = function(x){
var s=x[0], i=x.length;
while (--i) s *= x[i];
return s;
}

var funcName = arguments[0];
var ar = [];
for (var i=1, len=arguments.l ength; i<len; ++i) {
ar[ar.length] = arguments[i];
}
return this[funcName](ar);
}

alert(tunnel('s um', 1, 2, 3, 4)); /* 10 */
alert(tunnel('p roduct', 1, 2, 3, 4)); /* 24 */

Note that the function (e.g. sum) name needs to be passed as a string.

--
Rob

**Telmo Costa** · Feb 16 '06, 01:55 PM

Re: function and arguments as aguments

>[color=blue]
> How about:
>
> function tunnel()
> {
> this.sum = function(x){
> var s=x[0], i=x.length;
> while (--i) s += x[i];
> return s;
> }
> this.product = function(x){
> var s=x[0], i=x.length;
> while (--i) s *= x[i];
> return s;
> }
>
> var funcName = arguments[0];
> var ar = [];
> for (var i=1, len=arguments.l ength; i<len; ++i) {
> ar[ar.length] = arguments[i];
> }
> return this[funcName](ar);
> }
>
> alert(tunnel('s um', 1, 2, 3, 4)); /* 10 */
> alert(tunnel('p roduct', 1, 2, 3, 4)); /* 24 */
>
>
> Note that the function (e.g. sum) name needs to be passed as a string.
>[/color]

That won't do.

I'm building a XUL application (but could be HTML) and, at some point, I
need to start a couple of XMLHTTPRequest objects (using your examples,
sum and product will generate a XMLHTTPRequest object). Everything
worked ok, but now I have a restriction from the remote server: one
request at a time. I could make synchronous XMLHTTPRequests , but it will
froze the application.

So, I thought of a "tunnel" function that could work as a
synchronization point, where i build a queue of request and dispatch one
at a time. This way, the impact in the rest of the code is minimal.

**Thomas 'PointedEars' Lahn** · Feb 16 '06, 05:45 PM

Re: function and arguments as aguments

RobG wrote:
[color=blue]
> UnaCoder wrote:[color=green]
>> Well I thought there was and I researched java script to see if you can
>> invoke a string containing java script code. the solution that seemed
>> intuitive would be to do something like:
>>
>> function Tunnel() {
>> function_name= arguments[0];
>> arguments.shift (); args = arguments.join( );
>> eval function_name + "(" + args + ");";
>> }
>>
>> I didn't put any error checking in there, or test that code, but as far
>> as I know that should work =)[/color]
>
> Arguments is not an array, it's just a list[/color]

s/list/(Object) object/
[color=blue]
> with a few other properties that make it look a bit like an array.
> Consequently, it doesn't have split() or join() methods (and I don't
> think you can add them to its prototype).[/color]

Since `arguments' inherits directly from Object (ECMASCript 3 Final,
10.1.8), it is possible to add them, e.g.:

Object.prototyp e.join = function(delim)
{
var a = [];

for (var i = 0, len = this.length; i < len; i++)
{
a.push(this[i]);
}

return a.join(delim);
}

However, it is also an Object object without the ReadOnly attribute, so you
can add the methods to it instead, e.g.

arguments.join = function(delim)
{
/* see above */
}

The second approach would work for only one execution context, though, as
the `arguments' object is (re-)created and initialized every time control
enters an execution context for function code.

I have tested both approaches positive in Mozilla/5.0 (X11; U; Linux i686;
en-US; rv:1.8) Gecko/20060110 Debian/1.5.dfsg-4 Firefox/1.5.

PointedEars

**ron.h.hall@gmail.com** · Feb 16 '06, 07:15 PM

Re: function and arguments as aguments

Thomas 'PointedEars' Lahn wrote:
[...][color=blue]
> Since `arguments' inherits directly from Object (ECMASCript 3 Final,
> 10.1.8), it is possible to add them, e.g.:
>
> Object.prototyp e.join = function(delim)
> {
> var a = [];
>
> for (var i = 0, len = this.length; i < len; i++)
> {
> a.push(this[i]);
> }
>
> return a.join(delim);
> }
>[/color]
[...]

But since Array.prototype .join is generic (under ECMASCript 3), it
seems you should be able to use the built-in here, given that
'arguments': has a length and "numeric" properties:

Object.prototyp e.join = Array.prototype .join;

../rh

**Thomas 'PointedEars' Lahn** · Feb 16 '06, 11:45 PM

Re: function and arguments as aguments

ron.h.hall@gmai l.com wrote:
[color=blue]
> Thomas 'PointedEars' Lahn wrote:[color=green]
>> Since `arguments' inherits directly from Object (ECMASCript 3 Final,
>> 10.1.8), it is possible to add them, e.g.:
>>
>> Object.prototyp e.join = function(delim)
>> {
>> var a = [];
>>
>> for (var i = 0, len = this.length; i < len; i++)
>> {
>> a.push(this[i]);
>> }
>>
>> return a.join(delim);
>> }
>>[/color]
>
> But since Array.prototype .join is generic (under ECMASCript 3), it
> seems you should be able to use the built-in here, given that
> 'arguments': has a length and "numeric" properties:
>
> Object.prototyp e.join = Array.prototype .join;[/color]

Indeed. Thank you for pointing this out. When reading only

,-[ECMAScript Edition 3 Final]
|
| 15.4.4.5 Array.prototype .join (separator)
|
| The elements of the array are converted to strings, [...]
^^^^^^^^^^^^^^^ ^^^^^^^^^^

it is easy to overlook the following at the top of the next page
(PDF version):

| NOTE The join function is intentionally generic; it does not require that
| its `this' value be an Array object. Therefore, it can be transferred to
| other kinds of objects for use as a method. Whether the join function
| can be applied successfully to a host object is implementation-dependent.

(It should be noted *g* that there is such a NOTE for other methods of
Array.prototype too.)

The test case

Object.prototyp e.join = Array.prototype .join;
(function() { alert(arguments .join("x")); })(1, 2, 3); // "1x2x3"
alert({1: 2, 2: 3, length: 3}.join("x")); // "x2x3"

works in the following user agents:

- Mozilla Firefox 1.5.0.1
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.1) Gecko/20060209
Debian/1.5.dfsg+1.5.0. 1-2 Firefox/1.5.0.1

- Mozilla (Suite) 1.7.12
[Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20060205
Debian/1.7.12-1.1]

- Netscape Navigator 4.8
[Mozilla/4.8 [en] (X11; U; Linux 2.6.15.1-20060130.184242 +0100 i686)]

- Opera 8.51
[Opera/8.51 (X11; Linux i686; U; en)]

- Konqueror 3.5.1
[Mozilla/5.0 (compatible; Konqueror/3.5;
Linux 2.6.15.1-20060130.184242 +0100; X11; i686; de, en_US)
KHTML/3.5.1 (like Gecko) (Debian package 4:3.5.1-2)]

IE, Windows, and Mac testers, it's your turn :)

PointedEars

**RobG** · Feb 17 '06, 02:15 AM

Re: function and arguments as aguments

Thomas 'PointedEars' Lahn wrote:[color=blue]
> RobG wrote:
>
>[color=green]
>>UnaCoder wrote:
>>[color=darkred]
>>>Well I thought there was and I researched java script to see if you can
>>>invoke a string containing java script code. the solution that seemed
>>>intuitive would be to do something like:
>>>
>>>function Tunnel() {
>>> function_name= arguments[0];
>>> arguments.shift (); args = arguments.join( );
>>> eval function_name + "(" + args + ");";
>>>}
>>>
>>>I didn't put any error checking in there, or test that code, but as far
>>>as I know that should work =)[/color]
>>
>>Arguments is not an array, it's just a list[/color]
>
> s/list/(Object) object/[/color]

Yes, a list Object.

[color=blue][color=green]
>>with a few other properties that make it look a bit like an array.
>>Consequentl y, it doesn't have split() or join() methods (and I don't
>>think you can add them to its prototype).[/color]
>
> Since `arguments' inherits directly from Object (ECMASCript 3 Final,
> 10.1.8), it is possible to add them, e.g.:[/color]

The way I read the spec was that arguments shares the Object prototype,
which is null. I concluded that you couldn't add to it - clearly an
incorrect conclusion. :-x

I'll run the test in your other post later on a few Mac OS browsers.

--
Rob

VK · Feb 17 '06, 11:15 AM

Re: function and arguments as aguments

Thomas 'PointedEars' Lahn wrote:[color=blue]
> ron.h.hall@gmai l.com wrote:
>[color=green]
> > Thomas 'PointedEars' Lahn wrote:[color=darkred]
> >> Since `arguments' inherits directly from Object (ECMASCript 3 Final,
> >> 10.1.8), it is possible to add them, e.g.:
> >>
> >> Object.prototyp e.join = function(delim)
> >> {
> >> var a = [];
> >>
> >> for (var i = 0, len = this.length; i < len; i++)
> >> {
> >> a.push(this[i]);
> >> }
> >>
> >> return a.join(delim);
> >> }
> >>[/color]
> >
> > But since Array.prototype .join is generic (under ECMASCript 3), it
> > seems you should be able to use the built-in here, given that
> > 'arguments': has a length and "numeric" properties:
> >
> > Object.prototyp e.join = Array.prototype .join;[/color]
>
> Indeed. Thank you for pointing this out. When reading only
>
> ,-[ECMAScript Edition 3 Final]
> |
> | 15.4.4.5 Array.prototype .join (separator)
> |
> | The elements of the array are converted to strings, [...]
> ^^^^^^^^^^^^^^^ ^^^^^^^^^^
>
> it is easy to overlook the following at the top of the next page
> (PDF version):
>
> | NOTE The join function is intentionally generic; it does not require that
> | its `this' value be an Array object. Therefore, it can be transferred to
> | other kinds of objects for use as a method. Whether the join function
> | can be applied successfully to a host object is implementation-dependent.
>
> (It should be noted *g* that there is such a NOTE for other methods of
> Array.prototype too.)
>
> The test case
>
> Object.prototyp e.join = Array.prototype .join;
> (function() { alert(arguments .join("x")); })(1, 2, 3); // "1x2x3"
> alert({1: 2, 2: 3, length: 3}.join("x")); // "x2x3"
>
> works in the following user agents:
>
> - Mozilla Firefox 1.5.0.1
> Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.1) Gecko/20060209
> Debian/1.5.dfsg+1.5.0. 1-2 Firefox/1.5.0.1
>
> - Mozilla (Suite) 1.7.12
> [Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20060205
> Debian/1.7.12-1.1]
>
> - Netscape Navigator 4.8
> [Mozilla/4.8 [en] (X11; U; Linux 2.6.15.1-20060130.184242 +0100 i686)]
>
> - Opera 8.51
> [Opera/8.51 (X11; Linux i686; U; en)]
>
> - Konqueror 3.5.1
> [Mozilla/5.0 (compatible; Konqueror/3.5;
> Linux 2.6.15.1-20060130.184242 +0100; X11; i686; de, en_US)
> KHTML/3.5.1 (like Gecko) (Debian package 4:3.5.1-2)]
>
> IE, Windows, and Mac testers, it's your turn :)[/color]

It works in JScript 5.6 (IE 6.0)

For the purity of picture :-) one should say that in JScript
"arguments" is an objects with non-enumerable properties "length",
"callee", "caller" and "00"..."0X"
Besides that "00"..."0N of arguments" properties are *protected* so you
can access them only by numeric index, so say arguments[1] is really an
access to the property arguments['01'] which is not accessible
otherwise. Overall it looks like HTMLCollection where scring property
access is locked. That is the reason why it is stated in docs that
"arguments is not an array despite it looks like one" (because it's
indeed not).

**Duncan Booth** · Feb 17 '06, 11:55 AM

Re: function and arguments as aguments

Thomas 'PointedEars' Lahn wrote:
[color=blue]
> The test case
>
> Object.prototyp e.join = Array.prototype .join;
> (function() { alert(arguments .join("x")); })(1, 2, 3); // "1x2x3"
> alert({1: 2, 2: 3, length: 3}.join("x")); // "x2x3"
>
> works in the following user agents:
>
> - Mozilla Firefox 1.5.0.1
> Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.1) Gecko/20060209
> Debian/1.5.dfsg+1.5.0. 1-2 Firefox/1.5.0.1
>
> - Mozilla (Suite) 1.7.12
> [Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20060205
> Debian/1.7.12-1.1]
>
> - Netscape Navigator 4.8
> [Mozilla/4.8 [en] (X11; U; Linux 2.6.15.1-20060130.184242 +0100 i686)]
>
> - Opera 8.51
> [Opera/8.51 (X11; Linux i686; U; en)]
>
> - Konqueror 3.5.1
> [Mozilla/5.0 (compatible; Konqueror/3.5;
> Linux 2.6.15.1-20060130.184242 +0100; X11; i686; de, en_US)
> KHTML/3.5.1 (like Gecko) (Debian package 4:3.5.1-2)]
>
> IE, Windows, and Mac testers, it's your turn :)[/color]

It appears to also work on IE 5.5 and IE 6.

function and arguments as aguments

function and arguments as aguments

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