Node existence check for nthRoot about mathsteps

[evykassirer]

Sounds good! This should all go in hasUnsupportedNodes I think :)

[shirleymiao]

#121

[evykassirer]

done! thanks @shirleymiao

[kevinbarabash]

Does mathjs not return a parse error when it sees nthRoot( )?

[evykassirer]

it doesn't :(

I believe it's 'cause it parses it as a FunctionNode and those don't have to have arguments. This only becomes an error when you try to evaluate the FunctionNode and it treats it specifically as a root function

@josdejong thoughts?

also a fix here could be in hasUnsupportedNodes.js, make sure that nthroot nodes have exactly 1 or 2 arguments

[kevinbarabash]

Thinking about this some more – not returning a parse error makes sense b/c how many arguments nthRoot requires is a semantic issue. We could do some kind of semantic sanity check on the parse tree. It might also make sense to also check if the argument(s) produces a result within the reals, e.g. nthroot(-1,2).

[evykassirer]

(and this would make a great first PR ^^)