Make arithmetic operations n-ary when it makes sense

[gsimone]

eg:

// now
Mul(a, Mul(b, Mul(c, Mul(1, 3 )))
// then 
Mul(a, b, c, 1, 3 ) // becomes => a * b * c * 1. * 3.
Add(a, b, c, 1, 3 ) // becomes => a + b + c + 1. + 3.

[hmans]

What is the expected behavior for subtraction and division? Consider that

Sub(a, Sub(b, Sub(c, d)))

is equivalent to

a - (b - (c - d))

while this

Sub(a, b, c, d)

sort of implies

a - b - c - d

Thoughts?

[gsimone]

Probably should only be for commutative operations?

[hmans]

I think it'd be fine to have Sub(a, b, c, d) compile to a - b - c - d and leave it to documentation to explain how it's different from Sub(a, Sub(b, Sub(c, d))). (Same with division.) Would you see any issues with this?

[gsimone]

Expectations might be a problem, rather not have it for non-commutative operations than have a behaviour that's not immediately obvious - as it is for commutative