Block class to vm

[carver]

What was wrong?

Related to #599 & #507

• state shouldn't care about block_class at all
• variable mutation internal to method that applies transactions sequentially

How was it fixed?

• moved block_class to VM
• this concept of applying a series of data one on top of the other seems oft-repeated in blockchains, so made a reusable pipe_accumulator to handle this case, and hopefully others.

Cute Animal Picture

[carver]

This felt like a good thing that might make sense to reuse a lot.

The idea is that we care about two things when applying a sequence of transforms: the final state (note I mean state in a general way, not VMState), and the list of artifacts produced along the way. In the context of applying transactions, we care about the final header, and all the receipts/computations produced along the way.

So with two inputs, like this:

              input0                    input1
                 |                        |
                 v                        v
state0 --> transform() -- --state1--> transform() -- --state2-->
                         |                          |            
                         v                          v           
                     artifact1                  artifact2 

We want state2 and (artifact1, artifact2). The base case of "no inputs" should generate an output of state0 and (, ).

I'll put that ^ diagram in the comments before merging

---

On the name: I also sort of like the name pipe_map for this method. Any other suggestions?

[carver]

I'm going to drop this commit because I like the idea of the transform generating a state-diff better. I'll come back to it.

[pipermerriam]

Maybe

• accumulation_pipe
• pipe_and_accumulate
• transform_and_accumulate
• apply_and_accumulate

[pipermerriam]

https://github.com/carver/py-evm/blob/bb5b969c0fccb4a8a91dfbd75440e129b37aaa4d/evm/vm/state.py#L265-L327

Are you planning to address this section in a subsequent PR or is this a WIP?

[carver]

Since this PR got lighter without the pipe_accumulator stuff, I'll go ahead and add that now. Will ping when ready for review.

[carver]

Ok, ready for you @pipermerriam