Improve the `math` bif

There is an undocumented math bif that can be used to access the Math object in JS.

We need to write docs on it.

There is also a somewhat private, but accessible -math-prop bif, we could actually make it so math could be a shortcut both for the -math and -math-prop based on the number of arguments passed.

[juice49]

Hey @tjfwalker, bif means built in function—simply a function that is included in Stylus.

The math function accepts two arguments: a value to operate on, and a JavaScript math function to use. I have put some example on CodePen that demonstrate this.

For example, you could call Math.sqrt in the following way:

math(400, 'sqrt')

This function is limited to having one value passed, which means you can’t use a JavaScript math function that accepts/requires multiple values (Math.min, for example). It might be worth reconsidering the implementation to allow this.

[tjfwalker]

I’ve been trying to find documentation that explains the math() function used in this Codepen, http://codepen.io/kizu/pen/etmzx , without any luck. I finally found this issue, from nearly _two years ago_, stating that it’s *undocumented" BIF —built-in function. What’s the status on writing up the “math bif” documentation? How does it work, what are the args being passed to math(), et cetera? Thanks.