# Re: valarray

From: Maxim Nikulin <nikulin_at_gorodok.net>
Date: Thu, 27 Oct 2005 19:49:40 +0700

Dear Tomasz,

You wrote:
>
> Have a look at TVectorD if you meant multiplication of numbers.

I've done it already. Unfortunately I can't find an appropriate function or an operator.

Double_t operator* (const TVectorD &source1,const TVectorD &source2);

and other operators are suitable for linear algebra operations but not in my case. There are some methods similar to std::valarray operators

void TVectorD::AddSomeConstant(Double_t val, const TVectorD& select);

```TVectorD& TVectorD::Sqr();
TVectorD& TVectorD::Sqrt();
TVectorD& TVectorD::Invert(); // can be used instead of operator/()

```

However I don't see per element multiplication. Could you point me to the method producing the vector c as shown below

TVectorD a,b;
TVectorD c(a.GetNrows());
for (UInt_t i = 0; i < c.GetNrows(); ++i) {

c[i] = a[i]*b[i];
}

I'm really sorry if I missed it in the reference.

```--
Yours faithfully,
Maxim Nikulin

> Maxim Nikulin wrote:
>
>> Hi,
>>
>> Is there a native ROOT class similar to STL std::valarray template?
>> I'm interested in e.g. element to element multiplication operator
>> (c = a*b means c[i] = a[i]*b[i]). Actually I prefer STL classes but in
>> general ROOT behaves better with native classes.
>>
>> I found no valarray CINT library, although the headers are present.
>> I've managed to build a dictionary with subset of valarray functions
>> and operators but it's better to have the library "out of box". I
>> can't say that writing correct LinkDef.h file was trivial problem and
>> it's seems that generating dictionary for operators is missed in the
>> ROOT Users Guide.
>>
>> I'm using ROOT-5.05/01, 2005-10-12 CVS HEAD, Fedora Core 2 Linux on
>> Pentium IV PC. Of course I made cintdlls during ROOT installation.
>>
```
Received on Thu Oct 27 2005 - 14:49:51 MEST

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