// test_gcd.swift
//   compute greatest common divisor

print("test_gcd.swift running")

var a = 10
var b = 5
var a1 = 1
a1 = gcd(a,b)
print("a=\(a), b=\(b), a1=\(a1)")

a = 6
b = 4
a1 = gcd(a,b)
print("a=\(a), b=\(b), a1=\(a1)")

a = -3
b = -9
a1 = gcd(a,b)
print("a=\(a), b=\(b), a1=\(a1)")

print("test_gcp.swift finished")
  
func gcd(_ a:Int,_ b:Int) -> Int {
  var a1 = 0
  var b1 = 0
  var r  = 0
  var q  = 0
    
  if a == 0 || b == 0 {
    a1 = 1
    return 1
  }
  if abs(a) > abs(b) {
    a1 = abs(a)
    b1 = abs(b)
  }
  else {
    a1 = abs(b)
    b1 = abs(a)
  }
  r = 1
  while r != 0 {
    q = a1 / b1
    r = a1 - q * b1
    a1 = b1;
    b1 = r;
  }
  return a1
} // end gcd 

// end  test_gcd.swift