no way to decode program

[apoelstra]

It appears that there is no canonical way to decode a program as a CommitNode; the decode_program_fresh_witness function is private.

Also, despite having "program" in the name, it does not check that the decoded node is 1->1. It should.

[apoelstra]

Also decode_program_fresh_witness crashes if you give it the hex "3f0000ff0100000000000000000000001f0200000000000000db00000000000000050700".

[uncomputable]

We added this functionality to hal-simplicity a while back, using unit values as placeholders in the witness. You ended up (de)serializing RedeemNodes with dummy witnesses, but it was basically CommitNodes. I removed it today, but we could add something similar to rust-simplicity.

[apoelstra]

In #97 I fixed the issue, but I am going to do a followup PR that eliminates this logic entirely.

[uncomputable]

Isn't the canonical way CommitNode::decode()?

[apoelstra]

@uncomputable it could be, but CommitNode::decode() doesn't enforce that the root type is 1->1, nor should it, because it could be used to decode any expression.

I think we should change decode_program so it's the same as CommitNode::decode but also sets the root type.

[uncomputable]

This relates to #43 that we have no concept of "program" in the code as an "expression" of type 1 → 1. I'm not sure if it makes sense to decode arbitrary expressions. We could open another issue with the explicit goal of separating expressions from programs.

[apoelstra]

Near the bottom of #99 (which I should maybe split into multiple PRs) I add a decode_program method which basically just does CommitNode::decode followed by a typeck. I think having that method is all the "program" support that we need, and that that PR would close this issue.

[uncomputable]

Resolved by #99