Find and fix error message

[crozzer]

How do find and fix this error

/var/folders/4n/gyjwfhl56m57bjyl81mmfd_h0000gn/T//ccM61GdG.ltrans0.ltrans.o: In function loop': /private/var/folders/4n/gyjwfhl56m57bjyl81mmfd_h0000gn/T/.arduinoIDE-unsaved2024413-1006-1lqqyjz.79go/sketch_may13a/sketch_may13a.ino:30: undefined reference to IRrecv::decode(decode_results*)'
collect2: error: ld returned 1 exit status

exit status 1

Compilation error: exit status 1

[crozzer]

thank you for reply I've copied the code if it helps

/*
IR Receiver Demonstration 1

IR-Rcv-Demo1.ino

Demonstrates IR codes with IR Receiver

Displays results on Serial Monitor

DroneBot Workshop 2017

http://dronebotworkshop.com

*/

//Include IR Remote Library by Ken Shirriff

#include <IRremote.hpp>

//Define sensor pin

const int RECV_PIN = 4;

//Define IR Receiver and Results Objects

IRrecv irrecv(RECV_PIN);

decode_results results;

void setup(){

// Serial Monitor @ 9600 baud

Serial.begin(9600);

// Enable the IR Receiver

irrecv.enableIRIn();

}

void loop(){

if (irrecv.decode(&results)){

// Print Code in HEX

Serial.println(results.value, HEX);

irrecv.resume();

}

}