官术网_书友最值得收藏!

Scala idioms

When do we know a language? In English, when we say a penny for your thoughts, we are using an idiom. We can express ourselves more succinctly and natively using these. Beating around the bush is another one. If we pick up enough of these and hurl them around at times, this will makes us fluent.

It is almost the same with programming languages. You see a construct time and again and make use of notable features of a specific programming language. Here is a sample of idioms from a few prominent languages.

For example, here is an idiomatic Scala way to sum up two lists of numbers:

scala> val d1 = List(1, 2, 3, 4, 5)
d1: List[Int] = List(1, 2, 3, 4, 5)

scala> val d2 = List(11, 22, 33, 44, 55)
d2: List[Int] = List(11, 22, 33, 44, 55)

scala> (d1, d2).zipped map (_ + _)
res0: List[Int] = List(12, 24, 36, 48, 60)

We could do this in a roundabout way; however, note that your Scala colleagues would quickly comprehend what is happening. Try the following command:

scala> (1 to 100).map( _ * 2 ).filter(x => x % 3 == 0 && x % 4 == 0 && x % 5 == 0)
res2: scala.collection.immutable.IndexedSeq[Int] = Vector(60, 120, 180)

For numbers from 1 to 100, we multiply each number by 2. We select those numbers that are divisible by 3, 4, and 5.

Here we are chaining method calls together. Each method returns a new value. The input is left unmodified. The intermediate values are threaded from call to call.

We could also write the preceding command as follows

scala> val l1 = 1 to 100
… // output elided
scala> val l2 = l1.map(_ * 2)
 … // output elided
scala> val l3 = l2.filter(x => x % 3 == 0 && x % 4 == 0 && x % 5 == 0)
l3: scala.collection.immutable.IndexedSeq[Int] = Vector(60, 120, 180)

However, the fluent API style is more idiomatic.

Note

You can learn more about fluent interfaces at http://www.martinfowler.com/bliki/FluentInterface.html.

People relate easily to idiomatic code. When we learn and use various Scala idioms, we will write code in the Scala way.

主站蜘蛛池模板: 吴江市| 商南县| 万荣县| 彭山县| 郓城县| 玉环县| 新绛县| 泸定县| 五莲县| 景东| 布尔津县| 商洛市| 鄂州市| 广宗县| 民县| 榆中县| 营口市| 梓潼县| 喜德县| 丹凤县| 长白| 仪征市| 万安县| 衡南县| 英吉沙县| 永嘉县| 龙井市| 通江县| 武威市| 襄汾县| 望都县| 鹿邑县| 南澳县| 三门峡市| 梅河口市| 车险| 吐鲁番市| 大港区| 同仁县| 江门市| 靖安县|