How to avoid scientific notation and show full number instead?

Question

I have a below code in one of the library which is causing some numbers to get shown in the form of scientific notation.

T value = 0;

template<typename U> void process(U& buf, DataOption holder) const {
    if (holder == DataOption::TYPES) {
        switch (type_) {
        case teck::PROC_INT:
            buf << "{\"int\":" << value << "}";
            break;
        case teck::PROC_LONG:
            buf << "{\"long\":" << value << "}";
            break;
        case teck::PROC_FLOAT:
            buf << "{\"float\":" << value << "}";
            break;
        case teck::PROC_DOUBLE:
            buf << "{\"double\":" << value << "}";
            break;
        default:
            buf << "{\"" << type_ << "\":" << value << "}";
        }
    }
}

For some of the different cases above, "value" is coming in scientific notation. How can I avoid showing scientific notation and instead show full number? I did some research and I can use "std::fixed" but where I should be using this?

Answer 1

std::fixed works within the same stream, so this won't work in case you're working with a stateless stream

case teck::PROC_DOUBLE:
    buf << std::fixed;
    buf << "{\"double\":" << value << "}";

Instead it should be like this

case teck::PROC_DOUBLE:
    buf << "{\"double\":" << std::fixed << value << "}";

So your function can be simplified like this for better readability too

template<typename U> void process(U& buf, DataOption holder) const
{
    if (holder == DataOption::TYPES)
    {
        buf << "{\"";

        switch (type_)
        {
            case teck::PROC_INT:    buf << "int";    break;
            case teck::PROC_LONG:   buf << "long";   break;
            case teck::PROC_FLOAT:  buf << "float";  break;
            case teck::PROC_DOUBLE: buf << "double"; break;
            default:                buf <<  type_;
        }

        buf << "\":" << std::fixed << value << "}";
    }
}