Was confused about ∧ in the Yellow paper. Fix #50 - pass 2 new tests.…

… Only 1 arithmetic failure left.

VMTests.md

@@ -9,7 +9,7 @@ VMTests
 + add4.json OK
 + addmod0.json OK
 + addmod1.json OK
-- addmod1_overflow2.json Fail
++ addmod1_overflow2.json OK
 + addmod1_overflow3.json OK
 + addmod1_overflow4.json OK
 + addmod1_overflowDiff.json OK
@@ -135,7 +135,7 @@ VMTests
 + mulUnderFlow.json OK
 + mulmod0.json OK
 + mulmod1.json OK
-- mulmod1_overflow.json Fail
++ mulmod1_overflow.json OK
 + mulmod1_overflow2.json OK
 + mulmod1_overflow3.json OK
 + mulmod1_overflow4.json OK
@@ -185,9 +185,9 @@ VMTests
 + smod2.json OK
 + smod3.json OK
 + smod4.json OK
-- smod5.json Fail
++ smod5.json OK
 + smod6.json OK
-- smod7.json Fail
++ smod7.json OK
 + smod8_byZero.json OK
 + smod_i256min1.json OK
 + smod_i256min2.json OK
@@ -198,7 +198,7 @@ VMTests
 + sub3.json OK
 + sub4.json OK
 ```
-OK: 189/195 Fail: 5/195 Skip: 1/195
+OK: 193/195 Fail: 1/195 Skip: 1/195
 ## vmBitwiseLogicOperation
 ```diff
 + and0.json OK

nimbus/vm/forks/gas_costs.nim

@@ -183,13 +183,13 @@ template gasCosts(FeeSchedule: GasFeeSchedule, prefix, ResultGasCostsName: untyp
  gSreset = FeeSchedule[GasSreset]
 
  # Gas cost - literal translation of Yellow Paper
- result.gasCost = if value.isZero.not xor gasParams.s_isStorageEmpty:
+ result.gasCost = if value.isZero.not and gasParams.s_isStorageEmpty:
  gSet
  else:
  gSreset
 
  # Refund
- if value.isZero xor gasParams.s_isStorageEmpty:
+ if value.isZero and not gasParams.s_isStorageEmpty:
  result.gasRefund = static(FeeSchedule[RefundSclear])
 
  func `prefix gasLog0`(activeMemSize, requestedMemSize: Natural): GasInt {.nimcall.} =