Making vehicle stop in front of wall using stepper motor and ultrasonic (HELP)

this is the code i tried it with:

  ---------------------------------------------------
  //Pin 2 Step left
  //Pin 3 Direction left

  //Pin 4 Step Right
  //Pin 5 Direction Right

  //Pin 6 trigger Sonar
  //pin 7 sonar reciever

  -------------------------------------------------
  //Wheel travels 2,544 mm/step

byte stepL = 2;
byte dirL = 3;
byte stepR = 4;
byte dirR = 5;
byte trig = 6;
byte son = 7;
byte button = 8;
byte ledRed = 9;
byte ledGreen = 10;
byte ledBlue = 11;
int distance = 0;
int duration = 0;
boolean buttonRead = LOW;
int steps = 0;
boolean readOut = LOW;

#include <Stepper.h>         // steppers
Stepper links(200, 2, 3);
Stepper rechts(200, 4, 5);

void setup() {
  pinMode(2, OUTPUT);        
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, INPUT);
  pinMode(8, INPUT_PULLUP);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  left.setSpeed(200);           //set stepper speeds
  right.setSpeed(200);
}

void loop() {
  digitalWrite(trig, LOW);                    // check distance
  delayMicroseconds(2);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  duration = pulseIn(son, HIGH);
  distance = duration * 0.034 / 2;            

  buttonRead = digitalRead(button);           //check button
  if (buttonRead = LOW){
    readOut = HIGH;
  }

  if (distance <= 4) {                        // check distance/button
      steps = 200;
    }
    else {
      steps = 0;
      readOut == LOW;
    }
  left.step(-steps);                          //make steps
  right.step(steps);
}