pass an array throuh a function

**Leor Zolman** · Jul 22 '05, 11:32 AM

Re: pass an array throuh a function

On Tue, 25 May 2004 18:12:12 -0400, "Kenny" <lerameur@yah00 .c0m> wrote:
[snip]

I've replied to your identical post on alt.comp.lang.l earn.c-c++. Please do
not multi-post; if you /must/ post to multiple groups (and there's seldom
good reason to do so), at least "cross-post" by including all the groups in
your To: list at once.
Thanks,
-leor

--
Leor Zolman --- BD Software --- www.bdsoft.com
On-Site Training in C/C++, Java, Perl and Unix
C++ users: download BD Software's free STL Error Message Decryptor at:

STL Error Decryptor for C++

https://www.bdsoft.com/tools/stlfilt.html

An STL Error Decryptor for C++ by Leor Zolman of BD Software - available to download here

**Unforgiven** · Jul 22 '05, 11:32 AM

Re: pass an array throuh a function

Kenny wrote:[color=blue]
> Hello,
> can anyone tell me how to pass an array to a function ?
> I have this function , part of my class.
> It works if I do not put in int a[i] everywhere , but obviously , I
> need to add an array so I can keep everything neat and tidy, And to
> call the array whenever I want[/color]

Your code seems to suggest that a should not be an array of int, for one
thing, so that's wrong.

You could use something like this:
-----
void Setting::SetCYl inder(int r, int h, int s, int a[], int count)
{
for (int i=0; i<count; i++)
{
/* do something */
}
}
-----
The disadvantage is that this can lead to hard to trace bugs if you pass a
'count' value that's not the actual length of the array.

The safe way is to use std::vector instead of arrays:
-----
void Setting::SetCYl inder(int r, int h, int s, std::vector<int > a)
{
for (int i=0; i<a.length(); i++)
{
/* do something */
}
}
-----

--
Unforgiven

**Rolf Magnus** · Jul 22 '05, 11:32 AM

Re: pass an array throuh a function

Kenny wrote:
[color=blue]
> Hello,
> can anyone tell me how to pass an array to a function ?[/color]

You can't. You can - however - pass a pointer to the array's first
element or you can pass a reference to an array.
[color=blue]
> I have this function , part of my class.
> It works if I do not put in int a[i] everywhere , but obviously , I
> need to add an array so I can keep everything neat and tidy, And to
> call the array whenever I want
>
> thanks
> kenny
>
>
> void Setting::SetCyl inder(int r, int h, int s, int a[i])
> {
> int value;
> for (int i=0; i<count; i++)[/color]

Where do you get 'count' from?
[color=blue]
> {
> cout<<" Enter a time: " <<endl;
> cin>> value;
> a[i].hours = value;
>
> cout<<" Enter a minute: " <<endl;
> cin>> value;
> a[i].minutes = value;
>
> cout<<" Enter a second: " <<endl;
> cin>> value;
> a[i].seconds = value;
> }
> }[/color]

Either try:

void Setting::SetCyl inder(int r, int h, int s, int* a)

This will pass a pointer to the first element of the array. The rest can
stay as it was. But you might need to add an additional parameter to
pass the size.
Alternatively, if the size is fixed at compile time:

void Setting::SetCyl inder(int r, int h, int s, int (&a)[size])

with 'size' being the size of the array.

**Kenny** · Jul 22 '05, 11:32 AM

Re: pass an array throuh a function

I wil try that thanks,

I also get a syntax error at this line:

a[i].SetCylinder(20 ,30,40, a[] );

: : error C2059: syntax error : ']'

Know what that means ?

"Rolf Magnus" <ramagnus@t-online.de> wrote in message
news:c90ks2$37r $06$1@news.t-online.com...[color=blue]
> Kenny wrote:
>[color=green]
> > Hello,
> > can anyone tell me how to pass an array to a function ?[/color]
>
> You can't. You can - however - pass a pointer to the array's first
> element or you can pass a reference to an array.
>[color=green]
> > I have this function , part of my class.
> > It works if I do not put in int a[i] everywhere , but obviously , I
> > need to add an array so I can keep everything neat and tidy, And to
> > call the array whenever I want
> >
> > thanks
> > kenny
> >
> >
> > void Setting::SetCyl inder(int r, int h, int s, int a[i])
> > {
> > int value;
> > for (int i=0; i<count; i++)[/color]
>
> Where do you get 'count' from?
>[color=green]
> > {
> > cout<<" Enter a time: " <<endl;
> > cin>> value;
> > a[i].hours = value;
> >
> > cout<<" Enter a minute: " <<endl;
> > cin>> value;
> > a[i].minutes = value;
> >
> > cout<<" Enter a second: " <<endl;
> > cin>> value;
> > a[i].seconds = value;
> > }
> > }[/color]
>
>
> Either try:
>
> void Setting::SetCyl inder(int r, int h, int s, int* a)
>
> This will pass a pointer to the first element of the array. The rest can
> stay as it was. But you might need to add an additional parameter to
> pass the size.
> Alternatively, if the size is fixed at compile time:
>
> void Setting::SetCyl inder(int r, int h, int s, int (&a)[size])
>
> with 'size' being the size of the array.
>[/color]

**Alan Johnson** · Jul 22 '05, 11:32 AM

Re: pass an array throuh a function

Kenny wrote:[color=blue]
> Know what that means ?
>
> "Rolf Magnus" <ramagnus@t-online.de> wrote in message
> news:c90ks2$37r $06$1@news.t-online.com...
>[color=green]
>>Kenny wrote:
>>
>>[color=darkred]
>>>Hello,
>>>can anyone tell me how to pass an array to a function ?[/color]
>>
>>You can't. You can - however - pass a pointer to the array's first
>>element or you can pass a reference to an array.
>>
>>[color=darkred]
>>>I have this function , part of my class.
>>>It works if I do not put in int a[i] everywhere , but obviously , I
>>>need to add an array so I can keep everything neat and tidy, And to
>>>call the array whenever I want
>>>
>>>thanks
>>> kenny
>>>
>>>
>>>void Setting::SetCyl inder(int r, int h, int s, int a[i])
>>>{
>>> int value;
>>> for (int i=0; i<count; i++)[/color]
>>
>>Where do you get 'count' from?
>>
>>[color=darkred]
>>> {
>>> cout<<" Enter a time: " <<endl;
>>> cin>> value;
>>> a[i].hours = value;
>>>
>>> cout<<" Enter a minute: " <<endl;
>>> cin>> value;
>>> a[i].minutes = value;
>>>
>>> cout<<" Enter a second: " <<endl;
>>> cin>> value;
>>> a[i].seconds = value;
>>> }
>>>}[/color]
>>
>>
>>Either try:
>>
>>void Setting::SetCyl inder(int r, int h, int s, int* a)
>>
>>This will pass a pointer to the first element of the array. The rest can
>>stay as it was. But you might need to add an additional parameter to
>>pass the size.
>>Alternatively , if the size is fixed at compile time:
>>
>>void Setting::SetCyl inder(int r, int h, int s, int (&a)[size])
>>
>>with 'size' being the size of the array.
>>[/color]
>
> I wil try that thanks,
>
> I also get a syntax error at this line:
>
> a[i].SetCylinder(20 ,30,40, a[] );
>
> : : error C2059: syntax error : ']'
>[/color]

Quick array/pointer lesson:

1. The name of an array, with no subscript, will serve a pointer to the
first element in the array.

2. a[i], when 'a' is a pointer, is shorthand for: *(a + i) ... the
significance of this is that, if you have a pointer to the first element
in an array, you can access the ith element with a[i].

So ...

void Setting::SetCyl inder(int r, int h, int s, int* a, int count)
{
int i;
for (i = 0; i < count; i++)
a[i] = i; // or whatever you want to do.
}

To call this function:

Setting s;
int a[50];

s.SetCylinder(2 0, 30, 40, a, 50) ;

Alan

**John Harrison** · Jul 22 '05, 11:32 AM

Re: pass an array throuh a function

"Kenny" <lerameur@yah00 .c0m> wrote in message
news:KKQsc.3982 $9q1.3566@news2 0.bellglobal.co m...[color=blue]
> I wil try that thanks,
>
> I also get a syntax error at this line:
>
> a[i].SetCylinder(20 ,30,40, a[] );
>
> : : error C2059: syntax error : ']'
>
> Know what that means ?
>[/color]

It means a[] is illegal, why did you think it was ok? You use the name of
the array to stand for the array (but actually is is converted to a pointer
to the start of the array).

a[i].SetCylinder(20 ,30,40, a);

The subject of pointers and arrays is very confusing to a newbie, get a good
C++ book and read it carefully, remember its probably not saying what you
think its saying.

john

pass an array throuh a function

pass an array throuh a function

Comment

Comment

Comment

Comment

Comment

Comment