Provide a way to represent 1-(-1)

[kevinbarabash]

    var expr = new Expression("1");
    expr = expr.subtract(-1);
    console.log(expr.toString());

prints out 1+1 which is what I would expect looking at the code. It would be nice if subtraction could have a separate representation from adding the inverse. I'd like to use your library to create an interactive math widget. If users start with 1 and the action they take is to subtract -1 then I'd like them see 1-(-1) before giving them the option to rewrite it as 1+1. Not sure if this is something you'd want in algebra.js or not.

[nicolewhite]

Hey Kevin,

Yeah, that's not really supported out of the box since everything is automatically reduced and combined. I can't think of a way to accomplish what you want that isn't really hacky, given the current functionality.

I wonder if it would make sense to add a simplify argument or something to all of the operations. Something like:

var expr = new Expression(1);
expr = expr.subtract(-1, simplify=false)
console.log(expr.toString());

1 - (-1)

Then,

expr = expr.simplify()
console.log(expr.toString());

2

I think that would be really awesome functionality for the use case of building interactive tutorials. Just not sure how much work it involves. :)

[kevinbarabash]

After thinking about it a bit, this is probably an unreasonable request because it would probably require significant changes to the current data structures. It's probably best to leave things be with the current auto-simplify behavior.

[nicolewhite]

I don't think it's unreasonable. As I mentioned on Hacker News, I think interactive math widgets / tutorials is a great use case of the library and so I have no problem adding features to focus on that. I've created #4 for this. While this won't cover the specific case of displaying 1 - (-1) rather than 1 + 1, I think the changes to the code to allow unsimplified expressions will bring me closer to being able to do that.

[kevinbarabash]

Cool. I'll reopen this then.