Why does Scala support shadow variables? [closed]

by

Just as a reminder: A variable, method, or type is said to shadow another variable, method, or type of the same name when it is declared in an inner scope, making it impossible to refer to the outer-scope entity in an unqualified way (or, sometimes, at all). Scala, just like Java, allows shadowing.

One possible reason I could see is that in Scala, it is frequent to have many nested scopes, each of which is relatively short (compared to e.g. Java or C++). Indeed, a block can start anywhere where an expression is expected, thus starting a new scope. The use of the shadowing names in the inner scopes is thus, on average, closer to their declaration and less ambiguous.

Moreover, inline closures often lead the programmer to need new variable names in a scope that is already crowded. Allowing shadowing also allows to keep using descriptive names that are sufficiently to the point, even if they are the same as al already used name, instead of inventing other weird names — like prefixing them with my, local, or (worse) _ or single-letter names…

Shadowing becomes less of a problem with good IDEs which can e.g. highlight in your source code the declaration of, and the references to, the variable under the cursor.

Just my two cents here…

More Related Contents:

  1. What’s the difference between => , ()=>, and Unit=>
  2. What is the purpose of type ascriptions in Scala?
  3. What is the advantage of using abstract classes instead of traits?
  4. Split 1 column into 3 columns in spark scala
  5. Provide schema while reading csv file as a dataframe
  6. How to flatmap a nested Dataframe in Spark
  7. How to read files from resources folder in Scala?
  8. Scala return statements in anonymous functions
  9. Scala – printing arrays
  10. What is the difference between `##` and `hashCode`?
  11. Scala: Why does Seq.contains take an Any argument, instead of an argument of the sequence type?
  12. When to use val or def in Scala traits?
  13. How to add “provided” dependencies back to run/test tasks’ classpath?
  14. Cake pattern with overriding abstract type don’t work with Upper Type Bounds
  15. Overload constructor for Scala’s Case Classes?
  16. Scala Sets contain the same elements, but sameElements() returns false
  17. What is the type of a variable-length argument list in Scala?
  18. How do I iterate RDD’s in apache spark (scala)
  19. How to compute cumulative sum using Spark
  20. using variable length argument in scala
  21. Underscore in List.filter
  22. Add Number of days column to Date Column in same dataframe for Spark Scala App
  23. How to wait for several Futures?
  24. How do you define a local var/val in the primary constructor in Scala?
  25. Scala 2.10 reflection, how do I extract the field values from a case class, i.e. field list from case class
  26. assembly-merge-strategy issues using sbt-assembly
  27. Understanding the Aux pattern in Scala Type System
  28. Multiple parameter closure argument type not inferred
  29. How to create a Dataset of Maps?
  30. Spark ML VectorAssembler returns strange output

Leave a Comment