floatFractionalBits

pub inline fn floatFractionalBits(comptime T: type) comptime_int {
    comptime assert(@typeInfo(T) == .float);

    // standard IEEE floats have an implicit 0.m or 1.m integer part
    // f80 is special and has an explicitly stored bit in the MSB
    // this function corresponds to `MANT_DIG - 1' from C
    return switch (@typeInfo(T).float.bits) {
        16 => 10,
        32 => 23,
        64 => 52,
        80 => 63,
        128 => 112,
        else => @compileError("unknown floating point type " ++ @typeName(T)),
    };
}