ConditionalNode with custom types

[DavidMulder0]

Been trying to add a custom type, and for the most part it has been going okay, as so far everything has 'just' been a typed function that needed adding support for. How would one go about adding support for instanceOfACustomType ? 1 : 0?

[josdejong]

Thanks for your input. I'm not entirely sure what you mean. Do you mean to ask to define support for a new type? That can be done via typed.addType, there is an example here: https://mathjs.org/examples/advanced/custom_datatype.js.html.

typed.addType({
  name: 'ACustomType',
  test: (x) => x instancof ACustomType
})

[DavidMulder0]

Apologies for the confusion, my issue is that after adding a type exactly like that, how would one go about defining the check for that type to work with the ternary syntax? Basically the ConditionalNode function seems to just have inlined support for a couple of hardcoded types as far as I can tell: https://github.dev/josdejong/mathjs/blob/29abd1701b354e215cdeb8ef9dda57dfa16c78ee/src/expression/node/ConditionalNode.js#L41

[josdejong]

Ah, I understand the issue.

Thinking aloud here:

1. A bit of a hack: you can replace the method ConditionalNode.prototype._compile with your own, like

   math.ConditionalNode.prototype._compile = function (math, argNames) { 
     // ... your own logic here ...
   }

2. We can introduce a new function truthy in mathjs, move the logic of testCondition into it, and use the new function in the ConditionalNode. From there, it should be easier to extend the function truthy with support for a new data type.

What do you think?

[gwhitney]

Another possible way: if we separated in typed.js how to convert a value from one type to another, from whether to automatically do that to try to fulfill a typed-function signature, then a type could just specify its conversion to boolean, and ConditionalNode could just always ask typed to convert its first argument to boolean.