object basic54 {
def main(args: Array[String]): Unit = {
val arr = Array(1, 2, 3, 4)
// reduce === reduceLeft
// val rst = arr.reduceLeft( (x,y) => x - y )
val rst = arr.reduceRight( (x,y) => x - y )
println(s"rst = ${rst}")
}
}
```
```
