Sonar sensor to arduino to servo

Projects Programming
3 
#include <Servo.h>
const int trigger=3;
const int echo=2;
float distance;
float a,b,c,d,e;
Servo xServo;

void setup()
{
  Serial.begin(9600);
  pinMode(trigger,OUTPUT);
  pinMode(echo,INPUT);
  xServo.attach(10);
  xServo.write(0);
}

void loop()
{

  digitalWrite(trigger,LOW);
  delayMicroseconds(5);
  digitalWrite(trigger,HIGH);
  delayMicroseconds(10);
  digitalWrite(trigger,LOW);
 
  distance=pulseIn(echo,HIGH);
  distance=distance*0.0001657;
 
  Serial.println(distance);
  delay(50);
 
  xServo.write(0);
  delay(500);
  checkangle();
  xServo.write(45);
  delay(500);
  checkangle();
  xServo.write(90);
  delay(500);
  checkangle();
  xServo.write(135);
  delay(500);
  checkangle();
  xServo.write(180);
  delay(500);
  checkangle();
}
 
void checkangle()
{
  if (xServo.read() == 0)
  {
    distance = a;
    delay(10);
    Serial.println(a);
    delay(50);
  }
  else if (xServo.read()== 45)
  {
    distance = b;
    delay(10);
    Serial.println(b);
    delay(50);
  }
  else if (xServo.read() == 90)
  {
    distance = c;
    delay(10);
  }
  else if (xServo.read() == 135)
  {
    distance = d;
    delay(10);
  }
  else if (xServo.read() == 180)
  {
    distance = e;
    delay(10);
  }
}

Moderator edit: And now with added CODE TAGS

here is my code in storing the values into variables. but its not working. I just programmed it according to what i know.
Please help me..