[WIP] EIP-50 - Sigma 6.0

eip-0050.md

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+Sigma 6.0
+=========
+
+This EIP contains proposed changes for Ergo contractual layer, called Sigma. These changes are based on found issues 
+in the current version of Sigma, as well as feedback got from users, i.e. Ergo ecosystem developers.
+
+
+Activation 
+----------
+
+Rule 1011 should be replaced with another one, likely with the same rule but under different id.
+
+Features Set 
+------------
+
+* *.validatePoW* method of *Header* type to validate Autolykos2 proof of work done on header 
+
+issue: https://github.com/ScorexFoundation/sigmastate-interpreter/issues/958
+
+* implement conversion from Long-encoded nBits representation to BigInt (long.fromNBits method) and to nBits from BitInt (bigInt.toNBits method) 
+
+issue: https://github.com/ScorexFoundation/sigmastate-interpreter/issues/675
+
+PR: https://github.com/ScorexFoundation/sigmastate-interpreter/pull/962 (nbits encoding)
+
+
+* implement Boolean to Byte conversion (boolean.toByte method)
+
+issue: https://github.com/ScorexFoundation/sigmastate-interpreter/issues/931
+PR: https://github.com/ScorexFoundation/sigmastate-interpreter/pull/932
+
+* implement BigIntModQ type (unsigned bigints mod Q, where Q is the order of secp256k1 group)
+
+issue: https://github.com/ScorexFoundation/sigmastate-interpreter/issues/554
+
+
+* finish executeFromVar implementation
+
+issue: https://github.com/ScorexFoundation/sigmastate-interpreter/issues/443 , https://github.com/ScorexFoundation/sigmastate-interpreter/issues/612
+
+* support MethodCall encoding of Numeric methods
+
+issue: https://github.com/ScorexFoundation/sigmastate-interpreter/issues/667
+
+
+* Add Numeric.toBytes, .toBits
+
+issue: https://github.com/ScorexFoundation/sigmastate-interpreter/issues/486
+
+* Fix for downcasting BigInt to Long fails
+
+issue: https://github.com/ScorexFoundation/sigmastate-interpreter/issues/877
+
+
+* Lazy default evaluation for Option.getOrElse
+
+issue: https://github.com/ScorexFoundation/sigmastate-interpreter/issues/906
+
+* Implement Some and None as global methods 
+
+issue: https://github.com/ScorexFoundation/sigmastate-interpreter/issues/462
+
+* Serialize Option[T] in DataSerializer
+
+issue: https://github.com/ScorexFoundation/sigmastate-interpreter/issues/659
+
+
+
+
+How to add a new method
+-----------------------
+
+Here are instructions on how to add a (as 6.0 is heavily about adding new methods).
+
+Implementation:
+
+* Checkout new branch based on "v6.0.0" branch
+
+* Find appropriate type (e.g. *SBigInt*) to add a desirable method (e.g. *nbits*)
+
+* Add method description there and add description handle to *getMethods()* in a class \*Methods corresponding to the type (*SBigIntMethods* in our example), add *method_eval* to be used via reflection in the compiler
+
+* Add method implementation to corresponding type in *SigmaDsl.scala* 
+
+
+* Add method evaluation to *ErgoTreeEvaluator* interface and its instantiation *CErgoTreeEvaluator*
+
+* Add new method to reflection-related descriptions in *ReflectionData* (needed for compiler mostly?)
+
+* Add pattern matching in GraphBuilding.scala to the compiler to get support for the new method in ErgoScript, e.g.
+```
+case Select(obj, SBigIntMethods.ToNBits.name, _) if obj.tpe == SBigInt && VersionContext.current.isV6SoftForkActivated =>
+```
+
+* Add new method to *SigmaDslUnit.scala* / *SigmaDslImpl.scala* (needed for compiler only)
+
+
+Tests:
+
+
+* Add compilation test in *TestingInterpreterSpecification*
+
+* Add roundtrip test in *MethodCallSerializerSpecification*
+
+* Add evaluation test (see "nbits evaluation" test)
+
+
+
+How to add a new type
+---------------------
+
+[TODO: complete]