basic: Is it possible to define optional parameters in a method declaration? how?

[Juan]

Thanks,
Juan.

[benben]

But after some afterthoughts I reason that there are situations when/where
the use of params could be appropriate.

It is only telling people, "hey, you can pass in an array, but if you are
too lazy to start a new line to declare that array, don't bother then, just
pass in the collection as separate parameters."

ben

I swear to God that I NEVER used params in my formal projects. Yes you are
right, it leads to less elegant designs.

I thought the OP was requesting something like the ... operator in parameter list so I flip though the C# book and found it.

ben

As has been pointed out, your use of params is inappropriate. C# does not

support default arguments, ala C++, which I believe is what Juan was

asking.

--

Chris Rolon
"RCS" <rs****@gmail.c om> wrote in message
news:dY******** ***********@new ssvr19.news.pro digy.com...

This the most inappropriate use of params I've seen. I assumed there were people that did this sort of thing, but this is the first time I've seen.
This is *NOT* how you should use params. Can you? Yes. Should you? No.

In fact, if you are going to propose that, why not just have EVERY method

be

defined like this:
int Match(params object[] theobjects)
{ }

int Average(params object[] theobjects)
{ }

int ListNames(param s object[] theobjects)
{ }

Why even bother defining specific parameters? I'll tell you why -

because

it

gives the developer a firm/known interface to write to and gaurantees

the expected data types and number of parameters.

The point is, making a loosely-coupled interface like this is really,

really

asking for trouble - from the fact that it's not self-documenting, which leads to developer confusion and assumptions (which lead to bugs), to an inherent bug of what if you change the underlying behaviour - but don't need

to change the interface? That can and will likely lead to bugs with
applications that consume this object.

In other words, if I give you an object I made it has:

string CalculateItems( params object[] theobjects)

You immediately need more information: "What do I pass in there? Does the order matter? What kind of data types?". Versus if I gave you:

string CalculateItems (int[] ProductIDs)

Then it's very clear (read: "self-documenting") - that this takes an array of ProductIDs.. You see?
This is just bad, bad form, please don't encourage people to do this!! If you want loosely coupled, go write in VB6 and make everything a variant!! :-)

"benben" <be******@yahoo .com.au> wrote in message
news:%2******** ********@TK2MSF TNGP14.phx.gbl. ..
>I shall disagree with you. C# comes with even better support for variable > number of arguments. It is the params keyword:
>
> class Demo
> {
> double Average(params double[] numbers)
> {
> double total = 0;
>
> foreach (double i in numbers)
> {
> total += i;
> }
>
> return total / numbers.Length;
> }
>
> int Match(double target, double error, params double[]

candidates) > {
> for (int i = 0; i < candidates.Leng th; ++i)
> {
> if (target - candiates <= error)
> {
> return i;
> }
> }
>
> return -1;
> }
>
> string ListNames(param s object[] objs)
> {
> string result = "";
>
> foreach (object obj in objs)
> {
> result += obj.ToString();
> result += "\r\n";
> }
>
> return result;
> }
>
> void Main()
> {
> double x = Average(1, 2, 3, 4); // yield 2.5
> double y = Average(2, 3, 4, 5); // yield 3.5
>
> // using array directly
> double z = Average(double[] {3, 4, 5, 6}); // yield 4.5
>
> int a = Match(3.1415926 , 0.0001,
> 1.23456, 2.34567, 3.1416270, 4.7319032); // yield 2
>
> // just another version
> int b = Match(3.1415926 , 0.0001,
> double[]{1.23456, 2.34567, 3.1416270, 4.7319032});
>
> string whatever("ben", 1, Color.Black, new MyClass());
>
> // ...
> }
> }
>
>> No, C# does not give you the ability have optional parameters like

in C++

> or
>> VB. The best that you could do is function overloading, as Patrick
>> pointed
>> out.
>>
>> --
>>
>> Chris Rolon
>>
>> This posting is provided "AS IS" with no warranties, and confers no
> rights.
>>
>> "Patrick Altman" <pa**********@g mail.com> wrote in message
>> news:e9******** ******@tk2msftn gp13.phx.gbl...
>> > Yes. Just overload the method.
>> >
>> > public class MyClass
>> > {
>> > public void MyMethod(int x, int y)
>> > {
>> > ...
>> > }
>> >
>> > public void MyMethod(int x)
>> > {
>> > MyMethod(x, 0);
>> > }
>> > }
>> >
>> > Now you have a class with a "single" method, with two "options"

of how

>> > to call it.
>> >
>> > Hope that helps.
>> >
>> > Patrick Altman
>> > <><
>> >
>> >
>> > Juan wrote:
>> > > Thanks,
>> > > Juan.
>> > >
>> > >
>> >
>> > --
>> > --
>> > Patrick Altman
>> > <><
>>
>>
>
>
>

[Sean Hederman]

String.Format comes leaping to mind as a good example of the use of params.

"benben" <be******@yahoo .com.au> wrote in message
news:%2******** ********@TK2MSF TNGP10.phx.gbl. ..

But after some afterthoughts I reason that there are situations when/where
the use of params could be appropriate.

It is only telling people, "hey, you can pass in an array, but if you are
too lazy to start a new line to declare that array, don't bother then,
just
pass in the collection as separate parameters."

ben

I swear to God that I NEVER used params in my formal projects. Yes you
are
right, it leads to less elegant designs.

I thought the OP was requesting something like the ... operator in

parameter

list so I flip though the C# book and found it.

ben

> As has been pointed out, your use of params is inappropriate. C# does not > support default arguments, ala C++, which I believe is what Juan was

asking.

>
> --
>
> Chris Rolon
>
>
> "RCS" <rs****@gmail.c om> wrote in message
> news:dY******** ***********@new ssvr19.news.pro digy.com...
> > This the most inappropriate use of params I've seen. I assumed there

were

> > people that did this sort of thing, but this is the first time I've

seen.

> >
> > This is *NOT* how you should use params. Can you? Yes. Should you?
> > No.
> >
> > In fact, if you are going to propose that, why not just have EVERY

method

> be
> > defined like this:
> >
> >
> > int Match(params object[] theobjects)
> > { }
> >
> > int Average(params object[] theobjects)
> > { }
> >
> > int ListNames(param s object[] theobjects)
> > { }
> >
> > Why even bother defining specific parameters? I'll tell you why -

because

> it
> > gives the developer a firm/known interface to write to and gaurantees

the

> > expected data types and number of parameters.
> >
> > The point is, making a loosely-coupled interface like this is really,
> really
> > asking for trouble - from the fact that it's not self-documenting, which > > leads to developer confusion and assumptions (which lead to bugs), to an > > inherent bug of what if you change the underlying behaviour - but don't > need
> > to change the interface? That can and will likely lead to bugs with
> > applications that consume this object.
> >
> > In other words, if I give you an object I made it has:
> >
> > string CalculateItems( params object[] theobjects)
> >
> > You immediately need more information: "What do I pass in there? Does

the

> > order matter? What kind of data types?". Versus if I gave you:
> >
> > string CalculateItems (int[] ProductIDs)
> >
> > Then it's very clear (read: "self-documenting") - that this takes an

array

> > of ProductIDs.. You see?
> >
> >
> > This is just bad, bad form, please don't encourage people to do
> > this!!

If

> > you want loosely coupled, go write in VB6 and make everything a

variant!!

> > :-)
> >
> >
> >
> > "benben" <be******@yahoo .com.au> wrote in message
> > news:%2******** ********@TK2MSF TNGP14.phx.gbl. ..
> > >I shall disagree with you. C# comes with even better support for

variable

> > > number of arguments. It is the params keyword:
> > >
> > > class Demo
> > > {
> > > double Average(params double[] numbers)
> > > {
> > > double total = 0;
> > >
> > > foreach (double i in numbers)
> > > {
> > > total += i;
> > > }
> > >
> > > return total / numbers.Length;
> > > }
> > >
> > > int Match(double target, double error, params double[] candidates) > > > {
> > > for (int i = 0; i < candidates.Leng th; ++i)
> > > {
> > > if (target - candiates <= error)
> > > {
> > > return i;
> > > }
> > > }
> > >
> > > return -1;
> > > }
> > >
> > > string ListNames(param s object[] objs)
> > > {
> > > string result = "";
> > >
> > > foreach (object obj in objs)
> > > {
> > > result += obj.ToString();
> > > result += "\r\n";
> > > }
> > >
> > > return result;
> > > }
> > >
> > > void Main()
> > > {
> > > double x = Average(1, 2, 3, 4); // yield 2.5
> > > double y = Average(2, 3, 4, 5); // yield 3.5
> > >
> > > // using array directly
> > > double z = Average(double[] {3, 4, 5, 6}); // yield 4.5
> > >
> > > int a = Match(3.1415926 , 0.0001,
> > > 1.23456, 2.34567, 3.1416270, 4.7319032); // yield 2
> > >
> > > // just another version
> > > int b = Match(3.1415926 , 0.0001,
> > > double[]{1.23456, 2.34567, 3.1416270, 4.7319032});
> > >
> > > string whatever("ben", 1, Color.Black, new MyClass());
> > >
> > > // ...
> > > }
> > > }
> > >
> > >> No, C# does not give you the ability have optional parameters like in > C++
> > > or
> > >> VB. The best that you could do is function overloading, as Patrick
> > >> pointed
> > >> out.
> > >>
> > >> --
> > >>
> > >> Chris Rolon
> > >>
> > >> This posting is provided "AS IS" with no warranties, and confers
> > >> no
> > > rights.
> > >>
> > >> "Patrick Altman" <pa**********@g mail.com> wrote in message
> > >> news:e9******** ******@tk2msftn gp13.phx.gbl...
> > >> > Yes. Just overload the method.
> > >> >
> > >> > public class MyClass
> > >> > {
> > >> > public void MyMethod(int x, int y)
> > >> > {
> > >> > ...
> > >> > }
> > >> >
> > >> > public void MyMethod(int x)
> > >> > {
> > >> > MyMethod(x, 0);
> > >> > }
> > >> > }
> > >> >
> > >> > Now you have a class with a "single" method, with two "options" of > how
> > >> > to call it.
> > >> >
> > >> > Hope that helps.
> > >> >
> > >> > Patrick Altman
> > >> > <><
> > >> >
> > >> >
> > >> > Juan wrote:
> > >> > > Thanks,
> > >> > > Juan.
> > >> > >
> > >> > >
> > >> >
> > >> > --
> > >> > --
> > >> > Patrick Altman
> > >> > <><
> > >>
> > >>
> > >
> > >
> > >
> >
> >
>
>

[RCS]

Well yeah, there are definitely appropriate places for using params, but in
user functions as described, I don't think it's proper. In places like
print() or string.Format() it does make sense, because you specifically
don't care what or how many parameters are sent in.

In most everything the average developer does, this is NOT the case - that's
all I'm saying. I'm not saying params is inherently bad, just the overuse of
them in regular code where a cleaner alternative is available.
"benben" <be******@yahoo .com.au> wrote in message
news:OI******** ******@TK2MSFTN GP15.phx.gbl...

This the most inappropriate use of params I've seen. I assumed there were
people that did this sort of thing, but this is the first time I've seen.

This is *NOT* how you should use params. Can you? Yes. Should you? No.

It is quite up to the implementor to decide the STYLE of the interface. In
those C days, we were too familiar with the printf() function, which
exactly
takes variable parameters. They were designed and implemented and used,
now
it is up to you to critique the design. But anyway, it is an option.

It is true that the overuse of params will lead to ugly designs.

In fact, if you are going to propose that, why not just have EVERY method

be

defined like this:
int Match(params object[] theobjects)
{ }

int Average(params object[] theobjects)
{ }

int ListNames(param s object[] theobjects)
{ }

Because they won't make sense. Take the Average example. Its semantics
says
"calculate the average of a bundle of numbers", notice the "a bundle of
numbes", not necessarily "a bundle of objects, any objects".

Why even bother defining specific parameters? I'll tell you why - because

it

gives the developer a firm/known interface to write to and gaurantees the
expected data types and number of parameters.

The point is, making a loosely-coupled interface like this is really,

really

asking for trouble - from the fact that it's not self-documenting, which
leads to developer confusion and assumptions (which lead to bugs), to an
inherent bug of what if you change the underlying behaviour - but don't

need

to change the interface? That can and will likely lead to bugs with
applications that consume this object.

In other words, if I give you an object I made it has:

string CalculateItems( params object[] theobjects)

You immediately need more information: "What do I pass in there? Does the
order matter? What kind of data types?". Versus if I gave you:

the params operator is only used to expand an array at call site. so
instead
of passing an array as a single parameter, you now have a chance to pass
in
a number of parameters to make the invocation look more natural.

notice I didn't simple use params object[], so "what kind of data types"
are
answered in the declaration.

the order doesn't matter. Otherwise params won't be used here. What is the
difference of Average(1,2,3,4 ) and Average(2,4,1,3 )?

string CalculateItems (int[] ProductIDs)

Then it's very clear (read: "self-documenting") - that this takes an
array
of ProductIDs.. You see?
This is just bad, bad form, please don't encourage people to do this!! If
you want loosely coupled, go write in VB6 and make everything a variant!!
:-)

I don't encourage people to do this. I only treat the introduction of
params
as a syntactic sugar. notice that:

string CalculateItems (params int[] ProductIDs)

is just compatible with

string CalculateItems (int[] ProductIDs)

as I said, the additional params operator is only to allow the caller to
pass in an array without openning a new line to declare the array.

"benben" <be******@yahoo .com.au> wrote in message
news:%2******** ********@TK2MSF TNGP14.phx.gbl. ..

>I shall disagree with you. C# comes with even better support for
>variable
> number of arguments. It is the params keyword:
>
> class Demo
> {
> double Average(params double[] numbers)
> {
> double total = 0;
>
> foreach (double i in numbers)
> {
> total += i;
> }
>
> return total / numbers.Length;
> }
>
> int Match(double target, double error, params double[] candidates)
> {
> for (int i = 0; i < candidates.Leng th; ++i)
> {
> if (target - candiates <= error)
> {
> return i;
> }
> }
>
> return -1;
> }
>
> string ListNames(param s object[] objs)
> {
> string result = "";
>
> foreach (object obj in objs)
> {
> result += obj.ToString();
> result += "\r\n";
> }
>
> return result;
> }
>
> void Main()
> {
> double x = Average(1, 2, 3, 4); // yield 2.5
> double y = Average(2, 3, 4, 5); // yield 3.5
>
> // using array directly
> double z = Average(double[] {3, 4, 5, 6}); // yield 4.5
>
> int a = Match(3.1415926 , 0.0001,
> 1.23456, 2.34567, 3.1416270, 4.7319032); // yield 2
>
> // just another version
> int b = Match(3.1415926 , 0.0001,
> double[]{1.23456, 2.34567, 3.1416270, 4.7319032});
>
> string whatever("ben", 1, Color.Black, new MyClass());
>
> // ...
> }
> }
>
>> No, C# does not give you the ability have optional parameters like in C++ > or
>> VB. The best that you could do is function overloading, as Patrick
>> pointed
>> out.
>>
>> --
>>
>> Chris Rolon
>>
>> This posting is provided "AS IS" with no warranties, and confers no
> rights.
>>
>> "Patrick Altman" <pa**********@g mail.com> wrote in message
>> news:e9******** ******@tk2msftn gp13.phx.gbl...
>> > Yes. Just overload the method.
>> >
>> > public class MyClass
>> > {
>> > public void MyMethod(int x, int y)
>> > {
>> > ...
>> > }
>> >
>> > public void MyMethod(int x)
>> > {
>> > MyMethod(x, 0);
>> > }
>> > }
>> >
>> > Now you have a class with a "single" method, with two "options" of how >> > to call it.
>> >
>> > Hope that helps.
>> >
>> > Patrick Altman
>> > <><
>> >
>> >
>> > Juan wrote:
>> > > Thanks,
>> > > Juan.
>> > >
>> > >
>> >
>> > --
>> > --
>> > Patrick Altman
>> > <><
>>
>>
>
>
>