I am trying to avoid constructs like this:
val result = this.getClass.getSimpleName if (result.endsWith("$")) result.init else result
Ok, in this example the then
and else
branch are simple, but you can image complex ones. I built the following:
object TernaryOp { class Ternary[T](t: T) { def is[R](bte: BranchThenElse[T,R]) = if (bte.branch(t)) bte.then(t) else bte.elze(t) } class Branch[T](branch: T => Boolean) { def ?[R] (then: T => R) = new BranchThen(branch,then) } class BranchThen[T,R](val branch: T => Boolean, val then: T => R) class Elze[T,R](elze: T => R) { def :: (bt: BranchThen[T,R]) = new BranchThenElse(bt.branch,bt.then,elze) } class BranchThenElse[T,R](val branch: T => Boolean, val then: T => R, val elze: T => R) implicit def any2Ternary[T](t: T) = new Ternary(t) implicit def fct2Branch[T](branch: T => Boolean) = new Branch(branch) implicit def fct2Elze[T,R](elze: T => R) = new Elze(elze) }
Defined that, I can replace the above simple example with:
this.getClass.getSimpleName is {s: String => s.endsWith("$")} ? {s: String => s.init} :: {s: String => s}
But how can I get rid of the s: String =>
? I want something like that:
this.getClass.getSimpleName is {_.endsWith("$")} ? {_.init} :: {identity}
I guess the compiler needs the extra stuff to infer types.
The conditional (ternary) operator is the only JavaScript operator that takes three operands: a condition followed by a question mark ( ? ), then an expression to execute if the condition is truthy followed by a colon ( : ), and finally the expression to execute if the condition is falsy.
The conditional operator (? :) is a ternary operator (it takes three operands).
The conditional operator – also known as the ternary operator – is an alternative form of the if/else statement that helps you to write conditional code blocks in a more concise way. First, you need to write a conditional expression that evaluates into either true or false .
Yes, it was added in version 2.5.
From Tony Morris' Lambda Blog:
I hear this question a lot. Yes it does. Instead of
c ? p : q
, it is writtenif(c) p else q
.This may not be preferable. Perhaps you’d like to write it using the same syntax as Java. Sadly, you can’t. This is because
:
is not a valid identifier. Fear not,|
is! Would you settle for this?c ? p | q
Then you’ll need the following code. Notice the call-by-name (
=>
) annotations on the arguments. This evaluation strategy is required to correctly rewrite Java’s ternary operator. This cannot be done in Java itself.case class Bool(b: Boolean) { def ?[X](t: => X) = new { def |(f: => X) = if(b) t else f } } object Bool { implicit def BooleanBool(b: Boolean) = Bool(b) }
Here is an example using the new operator that we just defined:
object T { val condition = true import Bool._ // yay! val x = condition ? "yes" | "no" }
Have fun ;)
We can combine How to define a ternary operator in Scala which preserves leading tokens? with the answer to Is Option wrapping a value a good pattern? to get
scala> "Hi".getClass.getSimpleName |> {x => x.endsWith("$") ? x.init | x} res0: String = String scala> List.getClass.getSimpleName |> {x => x.endsWith("$") ? x.init | x} res1: String = List
Is this adequate for your needs?
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