DataWeave 2 - Generate Fibonacci sequence


In this post, we will see how to generate a Fibonacci sequence using DataWeave 2.

Fibonacci Sequence

Fibonacci number sequence is a series of numbers where each number is the sum of two preceding ones, starting from 0 and 1.

Fibonacci sequence with DataWeave

Generating Fibonacci sequence in DataWeave

We can generate Fibonacci sequence in DataWeave with a simple recursive function.

Table 1. Fibonacci Sequence
Script Output (application/json)
%dw 2.0
output application/json indent=false

fun fibonacci(limit:Number,series:Array<Number>) (1)
    = if (limit <= 0) series
        else fibonacci( limit - 1, series + (series[-1] + series[-2]))

fun fibonacci(limit:Number) = fibonacci(limit, [0, 1]) (2)
---
{
  limit10: fibonacci(10), (3)
  limit15: fibonacci(15, [13,21]) (4)
}
{
    "limit10": [0,1,1,2,3,5,8,13,21,34,55,89], (5)
    "limit15": [13,21,34,55,89,144,233,377,610,987,1597,2584,4181,6765,10946,17711,28657] (6)
}
1 fibonacci function computing the sequence with a given number count limit.
2 Overloaded fibonacci function to start with default 0 and 1 as starting.
3 Get 10 fibonacci sequence numbers start from default 0 and 1
4 Get 15 fibonacci sequence numbers after 13 and 21 sequential pair
5 Generated fibonacci for 10 numbers
6 Generated fibonacci for 15 numbers starting after 13 and 21

fibonacci function uses a tail-recursion approach to avoid running into recursion stack limit. It keeps calling itself by decreasing the limit by 1 and adding a new number at the end of series. New number is calculated as sum of the preceding two numbers - Hence the Fibonacci sequence output.

fun fibonacci(limit:Number,series:Array<Number>)
    = if (limit <= 0) series
        else fibonacci( limit - 1, series + (series[-1] + series[-2]))
What is 103rd number in a Fibonacci sequence? Try running fibonacci(100) using above function. Hint: It is a 21-digit number :).

Conclusion

That’s all for this short post. It is not so difficult to write different functions in DataWeave 2. Hopefully, you learned something new here.

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