Arduino Robot. a function-definition is not allowed here before '{' token The code is very messy. We have an L293D circuit which has two enable pins always on. We also have an LDR light sensor with two light resistors, one on the left and one on the right.

We are trying to make a line following robot

We are ambitious high school students.

// Use this code to test your motor with the Arduino board:

// if you need PWM, just use the PWM outputs on the Arduino
// and instead of digitalWrite, you should use the digitalWrite command


// --------------------------------------------------------------------------- Setup
void setup() {
{Serial.begin(9600);

// --------------------------------------------------------------------------- Motors
int motor_left[] = {2, 7};
int motor_right[] = {10, 15};
int LDR = 0;     //analog pin to which LDR is connected, here we set it to 0 so it means A0
int LDRValue = 0;      //that’s a variable to store LDR values
int light_sensitivity = 500;    //This is the approx value of light surrounding your LDR
int LDR2 = 0;     //analog pin to which LDR is connected, here we set it to 0 so it means A0
int LDR2Value = 0;      //that’s a variable to store LDR values
int light_sensitivity2 = 500;    //This is the approx value of light surrounding your LDR
int i;
for(i = 0; i &lt; 2; i++){
pinMode(motor_left[i], OUTPUT);
pinMode(motor_right[i], OUTPUT);
LDRValue = analogRead(LDR);     
    Serial.println(LDRValue);      


    if (LDRValue &lt; light_sensitivity); 
    Serial.println("wat");


}
// --------------------------------------------------------------------------- Loop


// --------------------------------------------------------------------------- Drive

void motor_stop(){
digitalWrite(motor_left[0], LOW); 
digitalWrite(motor_left[1], LOW); 

digitalWrite(motor_right[0], LOW); 
digitalWrite(motor_right[1], LOW);
delay(25);
}

void drive_forward(){
digitalWrite(motor_left[0], HIGH); 
digitalWrite(motor_left[1], LOW); 

digitalWrite(motor_right[0], HIGH); 
digitalWrite(motor_right[1], LOW); 
}

void drive_backward(){
digitalWrite(motor_left[0], LOW); 
digitalWrite(motor_left[1], HIGH); 

digitalWrite(motor_right[0], LOW); 
digitalWrite(motor_right[1], HIGH); 
}

void turn_left(){
digitalWrite(motor_left[0], LOW); 
digitalWrite(motor_left[1], HIGH); 

digitalWrite(motor_right[0], HIGH); 
digitalWrite(motor_right[1], LOW);
}

void turn_right(){
digitalWrite(motor_left[0], HIGH); 
digitalWrite(motor_left[1], LOW); 

digitalWrite(motor_right[0], LOW); 
digitalWrite(motor_right[1], HIGH); 
}
void loop() {
drive_forward();
delay(1000);
motor_stop();
Serial.println("1");

drive_backward();
delay(1000);
motor_stop();
Serial.println("2");

turn_left();
delay(1000);
motor_stop();
Serial.println("3");

turn_right();
delay(1000);
motor_stop();
Serial.println("4"); 

motor_stop();
delay(1000);
motor_stop();
Serial.println("5");
}
You need to look more closely at your braces. Use the auto-format tool (Ctrl+T) to help you. For example:

void setup() {
{Serial.begin(9600);

// --------------------------------------------------------------------------- Motors
int motor_left[] = {2, 7};
int motor_right[] = {10, 15};
int LDR = 0;     //analog pin to which LDR is connected, here we set it to 0 so it means A0
int LDRValue = 0;      //that’s a variable to store LDR values
int light_sensitivity = 500;    //This is the approx value of light surrounding your LDR
int LDR2 = 0;     //analog pin to which LDR is connected, here we set it to 0 so it means A0
int LDR2Value = 0;      //that’s a variable to store LDR values
int light_sensitivity2 = 500;    //This is the approx value of light surrounding your LDR
int i;
for(i = 0; i &lt; 2; i++){
pinMode(motor_left[i], OUTPUT);
pinMode(motor_right[i], OUTPUT);
LDRValue = analogRead(LDR);     
    Serial.println(LDRValue);      


    if (LDRValue &lt; light_sensitivity); 
    Serial.println("wat");


}   // &lt;------------------------------------ HERE 

// --------------------------------------------------------------------------- Loop


// --------------------------------------------------------------------------- Drive

void motor_stop(){


Where I marked "HERE" you are closing the for loop but you should also be closing setup.

You also have two opening braces here:

void setup() {
{Serial.begin(9600);


Proper indentation is very helpful for sorting out these sorts of issues.