template to let compiler generate zero

KIBO · 06-15-2009, 01:08 AM

How could I create a template to let the compiler generate a zero for all types?

My guess was the following but I cant get it to compile

Code:

template<typename T>
struct Zero
{
  static T Value;
};

template<>
struct Zero<float>
{
  static float Value;
};

It would be handy for algorithms like accumulate which often deduce the template parameter from the starting zero in the argument list.

Code:

template<typename T>
T Func(T *Chances, size_t Size)
{
  T Total = std::accumulate(Chances, Chances + Size, 0);

  // do other stuff
}

The '0' in accumulate makes the compiler generate an accumulate<int>, if it was 0.0 it would be double.

So what Id like is to be able to type:

Code:

template<typename T>
T Func(T *Chances, size_t Size)
{
  T Total = std::accumulate(Chances, Chances + Size, Zero<T>::Value);

  // do other stuff
}

so I can call Func with any type and the compiler chooses from the arguments from Func itself.

anon · 06-15-2009, 01:18 AM

Have you tried:

Code:

T Total = std::accumulate(Chances, Chances + Size, T());

KIBO · 06-15-2009, 02:43 AM

well no
does

Code:

double x = double()

create an x with 0.0 then?

it seems to work with VS2005 but im not sure if its standard?

anon · 06-15-2009, 03:10 AM

This is the way to obtain the default value for a type. For example, this is how a std::vector is filled with all zero's when you create a vector<int> with a size parameter.

KIBO · 06-15-2009, 03:51 AM

didnt know that. thanks!

no need for overcomplicated template stuff then

06-15-2009, 01:08 AM	#1
KIBO Registered User Join Date: Jan 2007 Posts: 223	template to let compiler generate zero How could I create a template to let the compiler generate a zero for all types? My guess was the following but I cant get it to compile Code: template<typename T> struct Zero { static T Value; }; template<> struct Zero<float> { static float Value; }; It would be handy for algorithms like accumulate which often deduce the template parameter from the starting zero in the argument list. Code: template<typename T> T Func(T Chances, size_t Size) { T Total = std::accumulate(Chances, Chances + Size, 0); // do other stuff } The '0' in accumulate makes the compiler generate an accumulate<int>, if it was 0.0 it would be double. So what Id like is to be able to type: Code: template<typename T> T Func(T Chances, size_t Size) { T Total = std::accumulate(Chances, Chances + Size, Zero<T>::Value); // do other stuff } so I can call Func with any type and the compiler chooses from the arguments from Func itself.
KIBO is offline

06-15-2009, 02:43 AM	#3
KIBO Registered User Join Date: Jan 2007 Posts: 223	well no does Code: double x = double() create an x with 0.0 then? it seems to work with VS2005 but im not sure if its standard?
KIBO is offline

06-15-2009, 03:51 AM	#5
KIBO Registered User Join Date: Jan 2007 Posts: 223	didnt know that. thanks! no need for overcomplicated template stuff then
KIBO is offline

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