How to convert a string representing decimal number in exponential form to float in Qt?

问题

I have some decimal numbers in a text file represented in exponential form Eg: 144.2e-3. I want to store the values in float. In qt it returns "0" when i directly use the "number.toFloat()" method. Please help.

回答1:

toFloat() should work. Check that your string contains only the number. If the string contains something else too, for example "144.2e-3 a", then the toFloat() returns 0. Note that also other numbers in the string will cause the conversion to fail, for example QString("144.2e-3 100").toFloat() will return 0.

Additional whitespace in the number string doesn't matter, but other characters do.

回答2:

value = 3.91e+01;
double doubleValue;
stringstream valuestream(value);
valuestream >> doubleValue;

Using a stringstream you can convert exponential number to the datatype we require.

回答3:

Use QString::toDouble.

Example:

bool ok;
float f = static_cast< float>( QString( "1234.56e-02" ).toDouble( &ok));

来源：https://stackoverflow.com/questions/3730594/how-to-convert-a-string-representing-decimal-number-in-exponential-form-to-float