Make private inputs explicit

[Schaeff]

Problem

The way private inputs are treated is different from public ones:

• Private inputs are implicit, public inputs are explicit:

def main(c):
  c == a * b
  return 1

• Public inputs are passed as arguments in compute-witness, while private inputs are passed interactively
• It makes it hard to use compute-witness programatically
• It gives no way to list private inputs without solving the R1CS

Solution

We think they should be explicit:

def main(c | a,b):
  c == a * b
  return 1

Roadmap

1. Make it possible to pass private inputs as arguments in compute-witness rather than interactively (the interactive mode should be activated by a flag)
2. Make it possible to specify explicit private inputs in .code files
3. Ban implicit private inputs from .code files

Thoughts welcome :)

[JacobEberhardt]

We'll just leave this here for a bit to collect input!

[nicola]

I like the idea, it's just that it looks kind of odd syntax.

What if you require main to have two only: (x, w) which are vectors of inputs? (I know this complicates syntax).

[Schaeff]

Yes I guess the syntax is up for debate. Vectors are not supported elsewhere so that could be confusing. Other ideas:

• (a,b)(c,d) unless higher order functions are on the roadmap
• (private a, public b, private c)
• other?

Also, I wonder if that should be defined only for main, or all functions. It doesn't sound necessary for other functions, however it could introduce a consistent notion of scope.

[nicola]

I like (private a, public b, private c), but I also like the experimental syntax

[PeterBorah]

+1 to some sort of explicit syntax. (a, b, private c, private d) is probably the most obvious/conservative choice, though I am ok with the | notation and the ()() notation as well.

[Schaeff]

(a, b, private c, private d) is being implemented in #15

[Schaeff]

Merged into develop