Parse handle_query prover functions.

[chriseth]

Parses query / prover functions of the form

 query |<i>| std::prover::handle_query(<Y>, <i>, match std::prover::eval(<pc>) {
   <value1> => std::prelude::Query::Output(std::convert::int::<fe>(std::prover::eval(<arg1>)), std::prover::eval(<arg2>)),
   <value2> => std::prelude::Query::Input(std::convert::int::<fe>(std::prover::eval(<arg1>)), std::convert::int::<fe>(std::prover::eval(<arg2>))),
   ...
   _ => std::prelude::Query::None,

i.e. the ones used for "free input" columns.

[pacheco]

"two two arguments"

[pacheco]

I think this comment is missing some context here (not sure what "two arguments" or "input columns" are referring to)... maybe it should be elsewhere or have a bit more context?

[pacheco]

very minor, but this way its always evaluating all three, instead of stopping on the first success... if the functions have the same signature, maybe its possible to do something like [try_func1, try_func2, try_func3].iter().map(|f| f(...))?