def step1ab(self):
        """step1ab() gets rid of plurals and -ed or -ing. e.g.

           caresses  ->  caress
           ponies    ->  poni
           ties      ->  ti
           caress    ->  caress
           cats      ->  cat

           feed      ->  feed
           agreed    ->  agree
           disabled  ->  disable

           matting   ->  mat
           mating    ->  mate
           meeting   ->  meet
           milling   ->  mill
           messing   ->  mess

           meetings  ->  meet
        """
        if self.b[self.k] == 's':
            if self.ends("sses"):
                self.k = self.k - 2
            elif self.ends("ies"):
                self.setto("i")
            elif self.b[self.k - 1] != 's':
                self.k = 1 - self.k
        if self.ends("eed"):
            if self.m() > 0:
                self.k = self.k - 1
        elif (self.ends("ed") or self.ends("ing")) and self.vowelinstem():
            self.k = self.j
            if self.ends("at"):
                self.setto("ate")
            elif self.ends("bl"):
                self.setto("ble")
            elif self.ends("iz"):
                self.setto("ize")
            elif self.doublec(self.k):
                self.k = self.k - 1
                ch = self.b[self.k]
                if ch == 'l' or ch == 's' or ch == 'z':
                    self.k = self.k + 1
            elif (self.m() == 1 and self.cvc(self.k)):
                self.setto("e")
dataset/ETHPy150Open CGATOxford/cgat/scripts/revigo.py/PorterStemmer.step1ab/swapped operands of `-`