TailRecursive (Groovy 5.0.6)
Description: declaration: package: groovy.transform, annotation type: TailRecursive

Package groovy.transform

# Annotation Type TailRecursive

@Retention(SOURCE) @Target(METHOD) public @interface TailRecursive
Method annotation used to transform methods with tail recursive calls into iterative methods automagically since the JVM cannot do this itself. This works for both static and non-static methods.

It allows you to write a method like this:

     import groovy.transform.TailRecursive
     class Target {
          @TailRecursive
          long sumUp(long number, long sum = 0) {
              if (number == 0)
                  return sum;
              sumUp(number - 1, sum + number)
          }
     }
     def target = new Target()
     assert target.sumUp(100) == 5050
     assert target.sumUp(1000000) == 500000500000 //will blow the stack on most machines when used without @TailRecursive

`@TailRecursive` is supposed to work in combination with `@CompileStatic`

Known shortcomings:

- Only non-void methods are currently being handled. Void methods will fail compilation.
- Only direct recursion (calling the exact same method again) is supported.
- Mixing of tail calls and non-tail calls is not possible. The compiler will complain if some recursive calls cannot be handled.
- Checking if a recursive call is really tail-recursive is not very strict. You might run into cases where non-tail calls will be considered tail calls.
- In the presence of method overloading and method overriding you might run into situations where a call is considered recursive although it really is not.
- Catching `Throwable` around a recursive might lead to problems
- Non trivial continuation passing style examples do not work.
- Probably many unrecognized edge cases.

More examples:

     import groovy.transform.TailRecursive

     @TailRecursive
     long sizeOfList(list, counter = 0) {
         if (list.size() == 0) {
             counter
         } else {
            sizeOfList(list.tail(), counter + 1)
         }
     }

     // Without @TailRecursive a StackOverFlowError
     // is thrown.
     assert sizeOfList(1..10000) == 10000

Since:
  2.3