Format decimal with comma and thousand with dot

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12

How can I format a float for the Brazilian value format(price)?

Example: in php number_format($float,2,',','.') separates decimal with comma and unit of thousand with dot.

c++ qt

  • You mean: use the dot as a thousand separator? (it doesn’t make much sense to use it as a ten separator)

  • Dot by 3 dec(unit). In the topic informs.

  • As I recall, the math was 3 tens = 30. I see no meaning and I do not know the meaning of "Point by 3 dozen (unity)" (what unity means in this context?).

  • 1

    3 tens multiplied is equivalent to a thousand. This is the most widely used naming convention (in English it would be "thousands separator"). I edited the question to use this convention, if this is incorrect just reverse the edit.

  • @mgibsonbr This correct! A unit of thousand or (unit).

2 answers

12

Use Qlocale

If the formatting you want is used in a particular language, you can format your number by setting the Qlocate (English) with the language containing the desired formatting:

// a definição actual em uso
QLocale loc = QLocale::system();

// Recolher a formatação de números utilizada para a língua Portuguesa
QLocale brasil(QLocale::Portuguese);
loc.setNumberOptions(brasil.numberOptions());

// Define como valor por defeito
QLocale::setDefault(loc);

From here the formatting of numbers should already be as used by the Portuguese language.

  • 1

    It worked, thank you.

  • I’m having another problem. The values are being rounded. Example 11.020,51 showcase 11.020,50. You know how I can add up the figures without rounding up?

  • @user628298 The best is to try to work with values in format inteiro and not float. As you have been asked here: http://answall.com/questions/5746/bestdatatypesshowto work with money

  • @Lucas Nunes I’ll take a look. Thank you.

  • @user628298 You can make use of the native functions of c++ ceil() or floor(). You can also use QString::number(sum, 'f', 1). See this documentation and this.

6

The solution using the standard C++ library looks like this:

First you need to create a specialization of the Std::numpunct class and overwrite two methods to implement the specific behavior for our currency.

#include <iostream>
#include <iomanip>
#include <locale>
using namespace std;

class BRL : public numpunct<char>
{
    protected:

    //separador de milhar
    virtual char do_thousands_sep() const
    {
        return ',';
    }

    //padrão de agrupamento dos milhares, de 3 em 3
    virtual std::string do_grouping() const
    {
        return "\03";
    }
};

Then to use the following is done:

int main(int argc, char* argv[]){
    float _valor = 1022.33;

    //instanciando um locale que utilizará a especialização de numpunct
    locale br(locale(), new BRL());

    //configurar no cout o locale que será utilizado nas formatações
    cout.imbue(br);

    //setprecistion() é necessário para configurar precisão de apenas duas casas decimais
    //fixed é necessário para que o valor não seja impresso como notação científica.
    cout << "R$ " << setprecision(2) << fixed <<  _valor;

    return 0;
}

The console output looks like this:

R$ 1,022.33

Full version on ideone.

  • In addition: You can see more options on how to change the parameters (comma to dot or as you prefer) in the class documentation: http://en.cppreference.com/w/cpp/locale/numpunct

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