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      std::setprecision

      De cppreference.com
      < cpp | io | manip

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      <tbody> </tbody>
      Definido no cabeçalho <iomanip>
      /*unspecified*/ setprecision( int n );
      Quando utilizado numa expressão out << setprecision(n) ou in >> setprecision(n), define o parâmetro do fluxo de precision out ou in exactamente n.
      Original:
      When used in an expression out << setprecision(n) or in >> setprecision(n), sets the precision parameter of the stream out or in to exactly n.
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      Parâmetros

      n -
      novo valor para a precisão
      Original:
      new value for precision
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      Valor de retorno

      Devolve um objecto de tipo não especificado de tal forma que se str é o nome de um fluxo de saída de std::basic_ostream<CharT, Traits> tipo ou um fluxo de entrada de std::basic_istream<CharT, Traits> tipo, então a expressão str << setprecision(n) str >> setprecision(n) ou se comporta como se o seguinte código foi executado:
      Original:
      Returns an object of unspecified type such that if str is the name of an output stream of type std::basic_ostream<CharT, Traits> or an input stream of type std::basic_istream<CharT, Traits>, then the expression str << setprecision(n) or str >> setprecision(n) behaves as if the following code was executed:
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      str.precision(n);

      Exemplo

      #include <iostream>
#include <iomanip>
#include <cmath>
#include <limits>
int main()
{
    const long double pi = std::acos(-1.L);
    std::cout << "default precision (6): " << pi << '\n'
              << "std::precision(10):    " << std::setprecision(10) << pi << '\n'
              << "max precision:         "
              << std::setprecision(std::numeric_limits<long double>::digits10)
              << pi << '\n';
}

      Saída: 

      default precision (6): 3.14159
std::precision(10):    3.141592654
max precision:         3.14159265358979324

      Veja também



      (C++11)
      (C++11)
      alterações de formatação utilizada para ponto flutuante de I / O
      Original:
      changes formatting used for floating-point I/O
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      (função) [edit]