How to declare a C++ function for Arduino code?

Question

I got the following Arduino code for receiving text from Bluetooth and display it back to a LCD display.

When Enter is inputted detectarClase() should be called with IP String as argument.

This is the .ino code:

#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
#include <string.h>

LiquidCrystal_I2C lcd(0x20,16,2); 

boolean borrar = false;
String IP;

String detectarClase(String ip) {

  char var[ip.length()]
  ip.toCharArray(var, ip.length());

  int num= atoi(var);  

  if (num < 127 ) 
    return "Clase A";
  if (num == 127 ) 
    return "Direccion reservada";
  if (num > 127 && num < 192   )
    return "Clase B";
  if (num >= 192 && num < 224  )
    return "Clase C";
  if (num >= 224 && num < 240  )
    return "Clase D";
  if (num >= 240 && num < 255  )
    return "Clase E";
}

void setup()
{
  lcd.init();
  lcd.backlight();
  pinMode(13,OUTPUT);
  Serial.begin(9600);
  Serial1.begin(9600);

}

void loop() {

  while (Serial1.available()) { 

    char caracter = Serial1.read(); //Comprobamos el caracter 

    switch(caracter) {

    default:
                if (borrar) { 
                              IP = ""; 
                              lcd.clear();
                }

                lcd.print(caracter);
                delay(125);
                borrar = false;

                IP.concat(caracter);
                break;  

    case '\r':                
    case 0x0F:
    case 0x0A:  
                borrar = true;
                lcd.print(detectarClase(IP));
                break;  

  } //fin switch

}//serial disponible


}//fin programa

When I try to compile I get the following output:

BluetoothLCD.cpp: In function ‘String detectarClase(String)’:
BluetoothLCD.cpp:17:3: error: expected initializer before ‘ip’
BluetoothLCD.cpp:19:25: error: ‘var’ was not declared in this scope

I really can't see how I should declare the function, how can I amend this?

Answer 1

Try

char var[100];

Arrays may need constant size at compile time. I see you have missed the ';' at the end of that line.