Add opcode 0x46 blockreward (#700)

EIPS/eip-698.md

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+---
+eip: 698
+title: OPCODE 0x46 BLOCKREWARD
+author: Cody Burns <dontPanic@codywburns.com>
+discussions-to: https://github.com/ethereum/EIPs/issues/698
+status: Draft
+type: Standards Track
+category: Core
+created: 2017-28-08
+---
+
+## Simple Summary
+
+This EIP adds an additional opcode to the EVM which will return a finalized blocks reward value. 
+
+## Abstract
+
+In the EVM, the 0x40 opcodes are reserved for `Block Information`. Currently reserved opcodes are:
+* `0X40 BLOCKHASH`
+* `0X41 COINBASE`
+* `0X42 TIMESTAMP`
+* `0X43 NUMBER`
+* `0X44 DIFFICULTY`
+* `0X45 GASLIMIT`
+
+This EIP would add an additional opcode, `0x46 BLOCKREWARD`, which would return the block reward for any finalized block. The finalized block reward would include the base reward, uncle payments, and gas.   
+
+## Motivation
+
+
+Per EIP-649 ( #669 ) periodic block reward reductions/variance are now planned in the roadmap, however, this EIP is consensus system agnostic and is most useful in decentralized pool operations and for any contract that benefits from knowing a block reward payout(i.e. Merge mined tokens) 
+
+## Specification
+
+After block `n` all clients should process opcode `0x46` as follows:  
+
+* Value: `0x46`
+* Mnemonic: `BLOCKREWARD`
+* δ:` 0` nothing removed from stack
+* α:`1` block reward added to stack
+* Description: `Get the block's reward emission` 
+* GasCost: `G<sub>base</sub>`
+
+Where:`µ'<sub>s</sub>[0] ≡ I<sub>HR</sub>`
+
+
+## Rationale
+
+### Contract Mining Pools
+
+For distributed consensus systems(staking pools and mining pools) ad hoc groups combine resources in order to reduce variance in payouts. Broadly, pool operations function by allowing a collective of  miners / stakers  to verify their contribution to solving PoW or staking share by periodically submitting solutions which are is representative of the miners probability of finding a true block. 
+
+In all these schemes `B` stands for a block reward minus pool fee and `p` is a probability of finding a block in a share attempt ( `p=1/D`, where `D` is current block difficulty).
+
+Some common methods of mining pool payout are pay-per-share, `R = B * p`, proportional [`R = B * (n/N)` where `n` is amount of a miners shares, and `N` is amount of all shares in this round.], and pay-per-last-N-shares [`R = B * (n/N)` where miner's reward is calculated on a basis of `N` last shares, instead of all shares for the last round]. All of these methods are predicated on knowing the block reward paid for a given block. In order to provide a trust minimized solution, `0x46` can be used to call a blocks reward for computing payouts.     
+
+### Merge mined tokens
+
+Contracts could create tokens which could be variably ‘minted’ as a function of block reward by calling `0x46`  
+
+## Backwards Compatibility
+
+
+### Currently deployed contracts
+
+No impact
+
+### Current clients
+
+This EIP would be incompatible with currently deployed clients that are not able to handle `0x46` and would process all transactions and block containing the opcode as invalid. 
+
+Implementation should occur as part of a coordinated hardfork.
+
+## Implementation
+
+
+## Further reading
+
+[Mining Pools](https://en.wikipedia.org/wiki/Mining_pool)
+
+The Yellow Paper Appendix H. Virtual Machine Specification section H.2
+
+## Copyright
+
+Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).