Simplify Custom Rules

[daz4126]

I'd like to add a couple of custom rules to the simplify function, one to stop it factorising expressions and another to stop negative terms being placed inside parentheses:

const equation = "-4x^1 - 4"
console.log(simplify(equation,rules).toString())
<<  "-(4 * (x + 1))"

const rules = ['(n1+n2)*n3 -> n1*n3 + n2*n3','-(n1) -> -n1']
console.log(simplify(equation,rules).toString())
<< "-4 x ^ 1 - 4"

Unfortunately these new rules seem to remove all the other default rules, so the power of -1 is now showing when previously it didn't. Is there any way of adding new rules while keeping the default rules?

I'd like the output to be: "-4x-4"

Thanks!

[josdejong]

The build in rules are exposes as math.simplify.rules, you can copy that array and add new entries to it (or mix and match the way you).

[daz4126]

Thanks, that's really useful to know.