int template argument

[Hicham Mouline]

hi,

I have a template function <typename cT, typename tT, int n>
{
.....
double array[n];

if (n==2)
binomial code
else if (n==3)
trinomial code (array[0] array[1] array[2])
else
.....


compiler tries to compile the "trinomial code" code even when the template
is instantiated with n=2,
and that gives warnings because of array[2]

Is there a way to make the compiler ignore the non-binomial code ?
some way with boost perhaps?

rds,

[Christian Hackl]

Re: int template argument

Hicham Mouline wrote:

I have a template function <typename cT, typename tT, int n>
{
....
double array[n];
>
if (n==2)
binomial code
else if (n==3)
trinomial code (array[0] array[1] array[2])
else
....
>
>
compiler tries to compile the "trinomial code" code even when the template
is instantiated with n=2,
and that gives warnings because of array[2]
>
Is there a way to make the compiler ignore the non-binomial code ?
some way with boost perhaps?

There's boost::array, which you could instead of the naked array.

http://www.boost.org/doc/html/array.html

--
Christian Hackl

[jason.cipriani@gmail.com]

Re: int template argument

"Christian Hackl" <hacki@sbox.tug raz.atwrote in message news:frp17l
$kfv$1@aioe.org ...

Hicham Mouline wrote:
>

>I have a template function <typename cT, typename tT, int n>
>{
>....
>double array[n];
>>
>if (n==2)
> binomial code
>else if (n==3)
> trinomial code (array[0] array[1] array[2])
>else
>....
>>
>>
>compiler tries to compile the "trinomial code" code even when the template
>is instantiated with n=2,
>and that gives warnings because of array[2]
>>
>Is there a way to make the compiler ignore the non-binomial code ?
>some way with boost perhaps?

>
There's boost::array, which you could instead of the naked array.
>
http://www.boost.org/doc/html/array.html

If the boost array is just a wrapper for a constant-sized array,
wouldn't a compiler that generates warnings about out-of-bounds
accesses complain when compiling the boost array template code, too?
Or is it just hidden behind a function parameter, in which case the
following would also kill the compiler warning in the original code:

double & access_array (double *a, int n) {
return a[n];
}

And then instead if:

....
else if (n==3) {
array[0] ...
array[1] ...
array[2] ...
}
....

It becomes:

....
else if (n==3) {
access_array(ar ray, 0) ...
access_array(ar ray, 1) ...
access_array(ar ray, 2) ...
}
....

Jason

[Kai-Uwe Bux]

Re: int template argument

Hicham Mouline wrote:

hi,
>
I have a template function <typename cT, typename tT, int n>
{
....
double array[n];
>
if (n==2)
binomial code
else if (n==3)
trinomial code (array[0] array[1] array[2])
else
....

You should overload the function for different values of n instead of using
an if statement to distinguish the cases. Alternatively, you can isolate
that piece of code into another function and overload that. Something like:

template < int n, typename cT, typename tT >
void polynomial_code ( ct & c, tT & t );

template < typename cT, typename tT>
void polynomial_code <2,cT,tT( ct & c, tT & t ) {
binomial code
}

template < typename cT, typename tT>
void polynomial_code <3,cT,tT( ct & c, tT & t ) {
trinomial code
}


template <typename cT, typename tT, int n>
...
polynomial_code <n>( ct_arg, tt_arg );
...

Maybe, I got the syntax slightly wrong, but I hope the idea is clear.


[snip]

Best

Kai-Uwe Bux

[Greg Herlihy]

Re: int template argument

On Mar 18, 10:26 am, "Hicham Mouline" <hic...@mouline .orgwrote:

I have a template function <typename cT, typename tT, int n>
{
....
double array[n];
>
if (n==2)
  binomial code
else if (n==3)
  trinomial code  (array[0] array[1] array[2])
else

Have you tried:

double array[n];

if (n==2)
binomial code
else if (n==3)
trinomial code (array[0] array[1] array[n-1])

Greg