argonaut | Purely functional JSON parser and library in scala | JSON Processing library

If you have a fixed number of values of different types, this is generally (in computer science and mathematics) called a "tuple", with a special name for when there are just two of them - a "pair".

JavaScript doesn't have a concept of a tuple, and admittedly it would make little sense in the absence of static types. So traditionally tuples in JavaScript are encoded as arrays.

But PureScript does have such concept! In the standard library it's called - surprise! - Tuple (and then there are variants for different number of elements - Tuple3, Tuple4, and so on)

And Argonaut follows the JavaScript convention: it encodes tuples as arrays. So if you just type your field as a Tuple Int String, it will work:

You should just define an EncodeJson instance for Magnitude and let Argonaut deal with the rest of the logic:

Use the Dijon library. It is a safe and efficient way to work with schema-less JSON using Scala these days.

Add dependency:

The problem (a NullPointerException) occurs within the createParser call made on this line:

EDIT: Scala functions are limited to an arity of 22. So this may just be your problem.

You need to use the "methods" supplied by Argonaut for constructing a JSON: := and ->:. For example:

I would probably skip coproduct SetOption representation on the PS side and just provide these two "dirty" constructors: