How to use "read_bool"?

[Zeh]

Hi, i am just a newbie trying learn D. But, i get having some 
trouble with "read_bool". More specifically on program of this 
lesson:

import std.stdio;
import std.conv;
import std.string;

void main()
{
     write("How many are we? ");
     int personCount;
     readf(" %s", &personCount);

     write("How many bicycles are there? ");
     int bicycleCount;
     readf(" %s", &bicycleCount);

     write("What is the distance to the beach? ");
     int distance;
     readf(" %s", &distance);

     bool existsCar = read_bool("Is there a car? ");
     bool existsLicense =
         read_bool("Is there a driver license? ");

When i try compile this, i get the following errors:

hello.d|43|Error: undefined identifier read_bool|
hello.d|44|Error: undefined identifier read_bool|
||=== Build finished: 2 errors, 0 warnings (0 minutes, 0 seconds) 
===|

So, someone know what's happening? What is the correct way to use 
the Read_bool?

Thanks for everyone!