String interpolation of variable value

Question

I want the variable value to be processed by string interpolation.

val temp = "1 to 10 by 2"
println(s"$temp")

output expected:

inexact Range 1 to 10 by 2

but getting

1 to 10 by 2

is there any way to get this way done?

EDIT The normal case for using StringContext is:

$> s"${1 to 10 by 2}"
inexact Range 1 to 10 by 2

This return the Range from 1 to 10 with the step value of 2.

And String context won't work on variable, so can there be a way I can do like

$> val temp = "1 to 10 by 2"
$> s"${$temp}"   //hypothetical

such that the interpreter will evaluate this as

s"${$temp}"  => s"${1 to 10 by 2}" => Range from 1 to 10 by step of 2 = {1,3,5,7,9}

Is there any logic in there? Do you need to detect if the "range is inexact"? If so, please describe that logic (and supply more examples). If not, s"inexact Range $temp". — Thilo
– Thilo, Commented Aug 12, 2020 at 10:33
So your question is very misleading. You want to compute arbitrary Scala code that comes from a file. That is basically the job for the REPL. You need to compile it and then run it. Or maybe not arbitrary code but rather a small grammar of just ranges? Then you need to write a small parser for that grammar. - In any case, this question should be closed since it was not clear and open a new one with all the details of what you really need to do and showing your attempt of solving it. — Luis Miguel Mejía Suárez
– Luis Miguel Mejía Suárez, Commented Aug 12, 2020 at 12:45

Michał Januszewski · Accepted Answer · 2020-08-12 12:50:10Z

1

By setting a string value to temp you are doing just that - creating a flat String. If you want this to be actual code, then you need to drop the quotes:

val temp = 1 to 10 by 2

Then you can print the results:

println(s"$temp")

This will print the following output string:

inexact Range 1 to 10 by 2

This is the toString(...) output of a variable representing a Range. If you want to print the actual results of the 1 to 10 by 2 computation, you need to do something like this:

val resultsAsString = temp.mkString(",")
println(resultsAsString)
> 1,3,5,7,9

or even this (watch out: here the curly brackets { } are used not for string interpolation but simply as normal string characters):

println(s"{$resultsAsString}")
> {1,3,5,7,9}

Edit If what you want is to actually interpret/compile Scala code on the fly (not recommended though - for security reasons, among others), then you may be interested in this: https://ammonite.io/ - Ammonite, Scala scripting

In any case, to interpret your code from a String, you may try using this: https://docs.scala-lang.org/overviews/repl/embedding.html

See these lines:

val scripter = new ScriptEngineManager().getEngineByName("scala")
scripter.eval("""println("hello, world")""")

edited Aug 12, 2020 at 12:50

answered Aug 12, 2020 at 11:57

Michał Januszewski

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1 Comment

Harshal Zope Over a year ago

Michal Januszewski , no, the value for val temp will be given from text file. What i want is val temp = "???" and it should process it based on whatever value it can be.

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