Scala流逐渐摆脱VAR

发布于 2025-02-01 00:04:07 字数 431 浏览 3 评论 0原文

我正在尝试通过从当前日期开始一个月来生成无限的日期列表，我想使用流进行此操作。

这是我到目前为止所做的：

import org.joda.time.LocalDate

var date = new LocalDate("2022-05-24")
val dateSeq = Seq(date)
val allDates = dateSeq.toStream ++ Stream.continually(dateSeq)
  .flatMap(ticks => ticks.map(_ => {
    date = date.minusMonths(1)
    date
  }))
allDates.take(5).toList

我的问题是，我使用var每次将当前日期降低一个月。

有什么方法可以摆脱var？

原文

I'm trying to generate an infinite list of dates by substracting one month from the current date, i want to do this using Streams.

Here's what i've done so far :

import org.joda.time.LocalDate

var date = new LocalDate("2022-05-24")
val dateSeq = Seq(date)
val allDates = dateSeq.toStream ++ Stream.continually(dateSeq)
  .flatMap(ticks => ticks.map(_ => {
    date = date.minusMonths(1)
    date
  }))
allDates.take(5).toList

My problem is that im using a var to decrement the current date by a month each time.

Is there any way to get rid of that var ?

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独木成林 2025-02-08 00:04:07

您只需要。术语而不是。

    vall allDates = Stream.iterate(LocalDate.now) { _.minusMonth(1) }

You just want .iterate rather than .continually:

    vall allDates = Stream.iterate(LocalDate.now) { _.minusMonth(1) }

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寻梦旅人 2025-02-08 00:04:07

使用@luis MiguelMejíaSuárez解决方案：

import org.joda.time.LocalDate

val numberOfMonthsBack = 5
val date = new LocalDate("2022-05-24")
val dateSeq = Seq(date)
val allDates = dateSeq.toStream ++ Stream.continually(dateSeq)
  .zip(Stream.from(1))
  .flatMap(ticks => 
    ticks._1.map(x => x.minusMonths(ticks._2))
  )
allDates
  .take(numberOfMonthsBack).toList

Using @Luis Miguel Mejía Suárez solution:

import org.joda.time.LocalDate

val numberOfMonthsBack = 5
val date = new LocalDate("2022-05-24")
val dateSeq = Seq(date)
val allDates = dateSeq.toStream ++ Stream.continually(dateSeq)
  .zip(Stream.from(1))
  .flatMap(ticks => 
    ticks._1.map(x => x.minusMonths(ticks._2))
  )
allDates
  .take(numberOfMonthsBack).toList

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