Why val declaration doesn't follow scala constants naming convention?

user_2037578 0
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In Scala val is used for creating constants and the naming convention for Scala Constants is to use UpperCamelCase convention. (https://docs.scala-lang.org/style/naming-conventions.html#constants-values-variable-and-methods)

A generalization for this rule should be all vals should be in UpperCamelCase.

i.e. if a variable is declared using val keyword its name should be in UpperCamelCase. However I see examples on Scala's website exploiting this rule.

What am I missing here?

coding-style constants naming-conventions scala
3 Answers

Put simply:

A constant only has one value while the program is running. It is either fixed at compile time, e.g. Pi, HoursInDay, or is an immutable value inside a top-level object.

A val is an immutable variable. It cannot be changed once it is set, but it may be set to different values each time the containing code is called.

user_76626700

Coding style suggests final constants to be uppercased:

if the member is final, immutable and it belongs to a package object or an object, it may be considered a constant

For example, note how scala.math.PI is defined as final:

@inline final val Pi = java.lang.Math.PI

vals inside objects are final in the sense they cannot be overridden so the following makes sense even though MyConstant it is not explicitly declared final:

object Container {
  val MyConstant = ...
}

If the val is not final, the style suggest lower case naming.

user_52050220

val in Scala is not only for defining Constants, it's also for defining Values. So, as Scala documentation states at https://docs.scala-lang.org/style/naming-conventions.html#constants-values-variable-and-methods :

For defining Constants you should use UpperCamelCase style where we tell these items Constant when:

If the member is final, immutable and it belongs to a package object or an object, it may be considered a constant.

For example:

object Container {
  val MyConstant = ...
}

While method, value and variable names should be in lowerCamelCase style like:

val myValue = ...
def myMethod = ...
var myVariable = ...
user_25084920
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