Make it possible for calculation of MathNode

[HK-SHAO]

Mathjs is so powerful!
I'm using it to do something I'm very interested in, a full platform computing APP.
I use the symbol '$' to keep an AST from being calculated.
It's like the Hold function in Mathematica or the hold function in MATLAB.
It would be interesting if a MathNode could also be computed!
It's like

$(sin(x))+$(cos(x))==$(sin(x)+cos(x))

[m93a]

Personally, I would love to have more operations for Nodes, see a related issue #1732. However the current dependency system isn't quite ready for all the circular dependencies this would bring (add(Node, Node) depends on Node, which depends on add(number, number)), see PR #1747 for the problem, and issue #1975 for a lengthy discussion on the possible fix of it.

If you have a proposal on how to implement this in a reasonable way that would work with the current dependency system, I'd love to hear it. Comments in the linked issues are also welcome :)

[josdejong]

Thanks for your suggestions @HK-SHAO , and good find of the open discussion/POC on this topic @m93a 👍

I'll close this PR in favor of #1732 to keep the discussion focused, please continue there.

[HK-SHAO]

Thanks for your suggestions @HK-SHAO , and good find of the open discussion/POC on this topic @m93a 👍

I'll close this PR in favor of #1732 to keep the discussion focused, please continue there.

Thank you for your attention 😆