IBP banding data system: Internal maintenance specification

In two cases of the MAPS 2004 format (at the beginning of the short tail, or at the end of the long tail), we expect either an ALIGNMENT_CHAR, which has no semantic import, or an OLD_PULL_INPUT character, which means we need to set the encounter object's PULLED_ATTR to the feather-pulled character.

# - - -   M a p s 2 0 0 4 E n c o u n t e r . s c a n O l d A l i g n

    def scanOldAlign(self, scan):
        '''Scan the MAPS 2004 alignment-or-feather-pulled field.

          [ scan is a Scan object ->
              if the line in scan starts with ALIGNMENT_CHAR ->
                scan  :=  scan advanced 1
              else if the line in scan starts with OLD_PULL_INPUT ->
                scan  :=  scan advanced 1
                self.(PULLED_ATTR)  :=  OLD_PULL_OUTPUT
              else ->
                Log()  +:=  error message
                raise SyntaxError ]
        '''
        if  scan.tabMatch(ALIGNMENT_CHAR):
            pass
        elif  scan.tabMatch(OLD_PULL_INPUT):
            setattr(self, PULLED_ATTR,
                    PulledField(self, OLD_PULL_OUTPUT))
        else:
            scan.syntax("Expecting alignment (%s) or "
                "feather-pulled (%s) character." %
                (ALIGNMENT_CHAR, OLD_PULL_INPUT))