Easy Question

I am trying to learn how to play with shift registers, and I have copied the code word for word from the arduino shift register tutorial. For some reason, it wants me to declare registerWrite?

sketch_jun28a.ino: In function 'void loop()':
sketch_jun28a:44: error: 'registerWrite' was not declared in this scope

what am I doing wrong here?

Edit: as per user request

/*
  Shift Register Example
 for 74HC595 shift register

 This sketch turns reads serial input and uses it to set the pins
 of a 74HC595 shift register.

 Hardware:
 * 74HC595 shift register attached to pins 2, 3, and 4 of the Arduino,
 as detailed below.
 * LEDs attached to each of the outputs of the shift register

 Created 22 May 2009
 Created 23 Mar 2010
 by Tom Igoe

 */

//Pin connected to latch pin (ST_CP) of 74HC595
const int latchPin = 8;
//Pin connected to clock pin (SH_CP) of 74HC595
const int clockPin = 12;
////Pin connected to Data in (DS) of 74HC595
const int dataPin = 11;

void setup() {
  //set pins to output because they are addressed in the main loop
  pinMode(latchPin, OUTPUT);
  pinMode(dataPin, OUTPUT);  
  pinMode(clockPin, OUTPUT);
  Serial.begin(9600);
  Serial.println("reset");
}

void loop() {
  if (Serial.available() > 0) {
    // ASCII '0' through '9' characters are
    // represented by the values 48 through 57.
    // so if the user types a number from 0 through 9 in ASCII, 
    // you can subtract 48 to get the actual value:
    int bitToSet = Serial.read() - 48;

  // write to the shift register with the correct bit set high:
    registerWrite(bitToSet, HIGH);
  }
}

To paraphrase a common internet saying:
"Code or it didn't happen."

This code?
And the rest of the code, the bit with the definition of the registerWrite function?

I got this error message

Binary sketch size: 2,810 bytes (of a 14,336 byte maximum)

it looked to me like it was two separate pieces of code. let me try it.

it looked to me like it was two separate pieces of code

...but with the name of the "missing" function clearly visible.

brain fart, my bad guys.