poly6.py

class Poly(object):
    def __init__(self, coef_initial=0, exponent_initial = 0, coefs=None):
        """ Create a polynomial with exactly one term, with coefficient
        coeff and exponent exponent, where coeff is an integer and exponent is a non-negative integer
        Defaults to the polynomial zero """
        if coefs == None:
            # if coeff == 0, then exponent should be 0
            if coef_initial == 0:
                exponent_initial = 0
            self.coefs = ([0]*exponent_initial)
            self.coefs.append(coef_initial)
        else:
            self.coefs = coefs
        
        """
            Permite criar o Poly de duas maneiras:\
                Poly(coef_initial=5, exponent_initial=3) - [0,0,0,5]
                Poly(coefs=[0,1,2,3]) - [0,1,2,3]
        """

    def format1(self, c, e):
        if e != 0:
            f = "{}x^{}".format(c,e)
        else:
            f = str(c)
        return f

    def __str__(self):
        # [7, 0, -5, 0, 3]
        s = ""
        for exp, c in list(enumerate(self.coefs))[::-1]:
            if c != 0:
                if exp == 0:
                    s += str(c) + " + "
                else:
                    s += str(c) + "x^" + str(exp) + " + "
        return s[:-2] #" 3x^4 + -5x^2 + 7 "
        
        """ Alternativa """
        return " + ".join([ self.format1(c,e) for e,c in enumerate(self.coefs) if c != 0 ][::-1])
        
    def isZero(self):
        """ Devolve se o polinomio e igual ao polinomio zero """
        return all([i == 0 for i in self.coefs])
    
    def coeff(self, exp=0):
        # p.coefs = [1,0,5,0,2,7] 
        # p.coeff[4] = 2
        if exp >= len(self.coefs):
            return 0
        else:
            return self.coefs[exp]        
        "Alternativa:"
        """
        try:
            return self.coefs[exp]
        except:
            return 0
        """
    
    def degree(self):
        v = len(self.coefs)-1
        ultimoIndice = v
        while self.coefs[ultimoIndice] == 0 and ultimoIndice > 0:
            v -= 1
            ultimoIndice -= 1
        return v

    def __add__(self, o):
        lg = self.coefs
        lp = o.coefs
        if len(lg) < len(lp):
            lg, lp = lp, lg
        nv = [ i for i in lg ]
        for i, v in enumerate(lp):
            nv[i] += v
            
        return Poly(coefs=nv)
        
        """
        # Alternativa
        ma = max(len(self.coefs), len(o.coefs))
        nl = []
        for i in range(ma): 
            v = 0
            if i < len(self.coefs):
                v += self.coefs[i]
            if i < len(o.coefs):
                v += o.coefs[i]
            nl.append( v )
        # Preeencher poly
        
        # Alternativa com map
        def f(a,b):
            if a == None:
                return b
            if b == None:
                return a
            return a+b
        nv = map(f, self.coefs, o.coefs)
        # Preeencher poly
        """
        
    def minus(self):
        nv = [ -e for e in self.coefs ]
        return Poly(coefs=nv)
        
    def __sub__(self, o):
        return self + o.minus()

    def __mul__(self, o):
        p = Poly()
        for e1, c1 in enumerate(self.coefs):
            for e2, c2 in enumerate(o.coefs):
                p = p + Poly(coef_initial=c1*c2, exp_initial=e1+e2)
        return p
            
    def evaluate(self, x):
        v = 0
        for e, c in enumerate(self.coefs):
            v += c * x**e
        return v

#print Poly(5,4) + Poly(3,2) # deve devolver - Poly.coefs = [0,0,3,0,5]

#print Poly(coefs=[0,0,1,0,5]).minus() # [0,0,1,0,5] -> [0,0,-1,0,-5]

print Poly(5,4) - Poly(3,2) # deve devolver - Poly.coefs = [0,0,-3,0,5]





"""

def testa(p):
    print "str():", str(p)
    print "isZero():", p.isZero()
    print "coeff(4):", p.coeff(4)
    print "degree():", p.degree()
    print "----"
    
testa(Poly(coef_initial=0, exponent_initial=0))
testa(Poly(coef_initial=5, exponent_initial=4))

p = Poly(coef_initial=5, exponent_initial=4)
p.coefs = [1,0,5,0,2,7]  # BATOTA!!!!!!!!!!!!!!
testa(p)

p_ = Poly(coef_initial=5, exponent_initial=4)
p_.coefs = [0,0,0,0,0,0]
testa(p_)

p_2 = Poly(coef_initial=5, exponent_initial=4)
p_2.coefs = [1,0,0,0,0,0]
testa(p_2)
        
"""