CODEWITHSUNDEEP
c++coding-stylenumeric-limits
vlad_tepesch
vlad_tepesch

Reputation: 6883

elegant way to get a variables limit

is there an better way to set a variables to one of its limits than 

varname = std::numeric_limits<decltype(varname)>::max();

especially when initializing

int64_t varname = std::numeric_limits<decltype(varname)>::max();

I normally do not want to use the type in such expressions since its easy to miss this if type is changed.

Upvotes: 3

Views: 2681

Answers (3)

Richard Hodges
Richard Hodges

Reputation: 69902

And just for completeness, skirting on the edge of legality:

#include <iostream>
#include <limits>

template<class T>
  T biggest(T&)
{
  return std::numeric_limits<T>::max();
}

int main()
{
  std::int64_t i = biggest(i);
  std::cout << i << std::endl;
  return 0;
}

Upvotes: 3

Cheers and hth. - Alf
Cheers and hth. - Alf

Reputation: 145359

Re

” I normally do not want to use the type in such expressions since its easy to miss this if type is changed.

that's easy:

auto varname = std::numeric_limits<int64_t>::max();

You can reduce the verbosity of std::numeric_limits in many ways, e.g. by an template alias or by defining a function template.

template< class Type >
using Limits_ = std::numeric_limits<Type>;

auto varname = Limits_<int64_t>::max();

or

template< class Type >
constexpr auto max_of() -> Type { return std::numeric_limits<Type>::max(); }

auto varname = max_of<int64_t>();

In C++14 and later you can make max_of a template variable, which for some reason that I've never seen explained, some people prefer.

Upvotes: 1

Jens
Jens

Reputation: 9416

What about auto?

auto varname = std::numeric_limits<int64_t>::max();

There is only one place mentioning the type.

Upvotes: 1

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