QString to double long float and long long int

Asked Dec 02 '17 at 14:22

Active Dec 02 '17 at 14:22

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Is it possible to convert the part before the decimal point to long long int and the part after the decimal point to long double float?

Example:

QString "1101.110";

and I would like to change that into two variables:

long long = 1101

long double = 0.110

I tried:

QString input = ui->inputbox->text();

long long whole = input.toInt();

double long fraction = input.toFloat();

If I input a number 110.10011:

whole outputs 0

fraction outputs 110.1 but I want it to output 0.10011

asked Dec 02 '17 at 14:22

Tomaž

The trivial solution is to subtract `whole` from fraction. Alternatively, a more straightforward approach is to just use `toFloat` and call `modf` on the result. – Matteo Italia Dec 02 '17 at 14:26
toInt() is probably failing to convert since it is a floating point number. If you used the parameter (pointer to bool) I expect the bool to be set to false. http://doc.qt.io/qt-5/qstring.html#toInt – drescherjm Dec 02 '17 at 14:31
What about splitting the string first ? – Xatyrian Dec 02 '17 at 14:38
@MatteoItalia how I convert double &intpart to int then? – Tomaž Dec 02 '17 at 14:55
1

`double val = input.toDouble();` will convert to double. `double intPart,fraction;` and `fraction = std::modf(val,&intPart);` – drescherjm Dec 02 '17 at 15:02
See the example here for modf usage: http://en.cppreference.com/w/cpp/numeric/math/modf – drescherjm Dec 02 '17 at 15:06
@Xatyrian how would I split the string? – Tomaž Dec 02 '17 at 16:05
`QString::split` – Xatyrian Dec 02 '17 at 16:34
1

A C solution: `long long ll = strtoll(input, &endptr, 0); double frac = strtod(endptr, &endptr);` – chux - Reinstate Monica Dec 02 '17 at 18:48

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