for loop not returning value in list after matching the expression

Question

I have used match expression using yield in for loop but I am not getting desired result

   val daysOfWeek = List("Mon","Tues","Wed","Thur","Fri","Sat","Sun")
        val day = "Mon"
         for (day <- daysOfWeek) yield
        {
          day match 
          {
            case "Mon" => "is boring"
            case otherDay => otherDay
              print(day)
          }
}

O/p of the above code is (TuesWedThurFriSatSun) but I want o/p like (is boringTuesWedThurFriSatSun)

How Can I achieve this ?

I think your problem is that the print is only executing in the case of other days. And also it is breaking the return type of all the expression to Any. What exactly do you want to do? — Luis Miguel Mejía Suárez
– Luis Miguel Mejía Suárez, Commented Sep 11, 2019 at 10:59

Mario Galic · Accepted Answer · 2019-09-11 11:06:50Z

1

Consider factoring out pattern matching into its own function

val boringDay: String => String = {
  case "Mon" => "is boring"
  case otherDay => otherDay
}

which can be used to transform the list

daysOfWeek.map(boringDay) // List(is boring, Tues, Wed, Thur, Fri, Sat, Sun)

and now use mkString to get a printable string

val output = daysOfWeek.map(boringDay).mkString("")
println(output)

which outputs

res1: String = is boringTuesWedThurFriSatSun

answered Sep 11, 2019 at 11:06

Mario Galic

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Comments

partha_devArch · Accepted Answer · 2019-09-11 10:56:10Z

0

The issue is that you are printing within the otherday case block, so you get that as output.

Here is what you want to achieve:

 val daysOfWeek = List("Mon","Tues","Wed","Thur","Fri","Sat","Sun")
 val day = "Mon"
 for (day <- daysOfWeek) yield
 {
     val output = day match
     {
        case "Mon" => "is boring"
        case otherDay => otherDay
     }
     print(output)
 }

Output:

is boringTuesWedThurFriSatSun

answered Sep 11, 2019 at 10:56

partha_devArch

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1 Comment

Luis Miguel Mejía Suárez Over a year ago

If you are yielding an Unit. It would be better yo just use the foreach syntax.

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