question: private static boolean isNaturalDocOrder ( Compiler compiler , int stepOpCodePos , int stepIndex , int analysis ) throws javax . xml . transform . TransformerException { if ( canCrissCross ( analysis ) ) return false ; if ( isSet ( analysis , BIT_NAMESPACE ) ) return false ; if ( isSet ( analysis , BIT_FOLLOWING | BIT_FOLLOWING_SIBLING ) && isSet ( analysis , BIT_PRECEDING | BIT_PRECEDING_SIBLING ) ) return false ; int stepType ; int stepCount = 0 ; boolean foundWildAttribute = false ; int potentialDuplicateMakingStepCount = 0 ; while ( OpCodes . ENDOP != ( stepType = compiler . getOp ( stepOpCodePos ) ) ) { stepCount ++ ; switch ( stepType ) { case OpCodes . FROM_ATTRIBUTES : case OpCodes . MATCH_ATTRIBUTE : if ( foundWildAttribute ) return false ; String localName = compiler . getStepLocalName ( stepOpCodePos ) ; if ( localName . equals ( "*" ) ) { foundWildAttribute = true ; } break ; case OpCodes . FROM_FOLLOWING : case OpCodes . FROM_FOLLOWING_SIBLINGS : case OpCodes . FROM_PRECEDING : case OpCodes . FROM_PRECEDING_SIBLINGS : case OpCodes . FROM_PARENT : case OpCodes . OP_VARIABLE : case OpCodes . OP_EXTFUNCTION : case OpCodes . OP_FUNCTION : case OpCodes . OP_GROUP : case OpCodes . FROM_NAMESPACE : case OpCodes . FROM_ANCESTORS : case OpCodes . FROM_ANCESTORS_OR_SELF : case OpCodes . MATCH_ANY_ANCESTOR : case OpCodes . MATCH_IMMEDIATE_ANCESTOR : case OpCodes . FROM_DESCENDANTS_OR_SELF : case OpCodes . FROM_DESCENDANTS : if ( potentialDuplicateMakingStepCount > 0 ) return false ; potentialDuplicateMakingStepCount ++ ; case OpCodes . FROM_ROOT : case OpCodes . FROM_CHILDREN : case OpCodes . FROM_SELF : if ( foundWildAttribute ) return false ; break ; default : throw new RuntimeException ( XSLMessages . createXPATHMessage ( XPATHErrorResources . ER_NULL_ERROR_HANDLER , new Object [ ] { Integer . toString ( stepType ) } ) ) ; } int nextStepOpCodePos = compiler . getNextStepPos ( stepOpCodePos ) ; if ( nextStepOpCodePos < 0 ) break ; stepOpCodePos = nextStepOpCodePos ; } return true ; }
target:  Tell if the pattern can be 'walked' with the iteration steps in natural  document order, without duplicates.