Пример #1
0
    def __init__(self, numbers_to_use, **options):
        super().setup("minimal", **options)
        super().setup("numbers", nb=numbers_to_use, **options)
        super().setup("nb_variants", nb=numbers_to_use, **options)

        degrees1 = [0, 1]
        degrees2 = [0, 1]
        random.shuffle(degrees1)
        random.shuffle(degrees2)

        weighted_signs = [('+', 19), ('-', 1)]
        weighted_signs = [
            val for val, cnt in weighted_signs for i in range(cnt)
        ]
        signs = ['+', '-']

        self.expandable = Expandable(
            (Polynomial([
                Monomial(
                    (random.choice(weighted_signs), self.nb1, degrees1.pop())),
                Monomial((random.choice(signs), self.nb3, degrees1.pop()))
            ]),
             Polynomial([
                 Monomial((random.choice(weighted_signs), self.nb2,
                           degrees2.pop())),
                 Monomial((random.choice(signs), self.nb4, degrees2.pop()))
             ])))
        self.expression = Expression(shared.number_of_the_question,
                                     self.expandable)
        self.expression_str = self.expression.printed
        shared.number_of_the_question += 1
Пример #2
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def test_eq11_autoresolution():
    """Is this Equation correctly auto-resolved?"""
    eq = Equation((Polynomial([Monomial(
        ('+', 5, 0)), Monomial(
            ('-', 1, 1))]), Polynomial([Monomial(('+', 5, 1))])),
                  number=1)
    assert eq.auto_resolution() == wrap_nb('$(\\text{E}_{1}): $'
                                           '\[5-x=5x\]'
                                           '\[-x-5x=-5\]'
                                           '\[(-1-5)x=-5\]'
                                           '\[-6x=-5\]'
                                           '\[x=\\frac{-5}{-6}\]'
                                           '\[x=\\frac{5}{6}\]')
Пример #3
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def test_eq8_autoresolution():
    """Is this Equation correctly auto-resolved?"""
    eq = Equation(
        (Polynomial([Monomial(
            ('+', 4, 1)), Monomial(('+', 2, 0))]),
         Polynomial([Monomial(
             ('-', 3, 0)), Monomial(('+', 2, 1))])),
        number=1)
    assert eq.auto_resolution() == wrap_nb('$(\\text{E}_{1}): $'
                                           '\[4x+2=-3+2x\]'
                                           '\[4x-2x=-3-2\]'
                                           '\[(4-2)x=-5\]'
                                           '\[2x=-5\]'
                                           '\[x=-\\frac{5}{2}\]')
Пример #4
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def test_eq9_autoresolution():
    """Is this Equation correctly auto-resolved?"""
    eq = Equation(
        (Polynomial([Monomial(
            ('-', 2, 1)), Monomial(('+', 5, 0))]),
         Polynomial([Monomial(
             ('+', 3, 1)), Monomial(('-', 4, 0))])),
        number=1)
    assert eq.auto_resolution() == wrap_nb('$(\\text{E}_{1}): $'
                                           '\[-2x+5=3x-4\]'
                                           '\[-2x-3x=-4-5\]'
                                           '\[(-2-3)x=-9\]'
                                           '\[-5x=-9\]'
                                           '\[x=\\frac{-9}{-5}\]'
                                           '\[x=\\frac{9}{5}\]')
Пример #5
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def test_eq13_autoresolution():
    """Is this Equation correctly auto-resolved?"""
    eq = Equation(
        (Polynomial([Monomial(
            ('+', 1, 1)), Monomial(('+', 5, 0))]),
         Polynomial([Monomial(
             ('+', 1, 1)), Monomial(('+', 2, 0))])),
        number=1)
    assert eq.auto_resolution() == wrap_nb('$(\\text{E}_{1}): $'
                                           '\[x+5=x+2\]'
                                           '\[x-x=2-5\]'
                                           '\[(1-1)x=-3\]'
                                           '\[0x=-3\]'
                                           '\[0=-3\]'
                                           'This equation has no solution.'
                                           '\\newline ')
Пример #6
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def expI():
    t = Sum([Monomial(('+', 4, 1)),
             Expandable((Monomial(('+', 1, 0)),
                         Polynomial([Monomial(('-', 15, 1)),
                                     Monomial(('+', 8, 0)),
                                     Monomial(('-', 5, 1))])))])
    return Expression("I", t)
Пример #7
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def test_eq10_autoresolution():
    """Is this Equation correctly auto-resolved?"""
    eq = Equation(
        (Polynomial([Monomial(
            ('+', 5, 0)), Monomial(('+', 4, 1))]),
         Polynomial([Monomial(
             ('-', 20, 1)), Monomial(('+', 3, 0))])),
        number=1)
    assert eq.auto_resolution() == wrap_nb('$(\\text{E}_{1}): $'
                                           '\[5+4x=-20x+3\]'
                                           '\[4x+20x=3-5\]'
                                           '\[(4+20)x=-2\]'
                                           '\[24x=-2\]'
                                           '\[x=-\\frac{2}{24}\]'
                                           '\[x=-\\frac{\\bcancel{2}}'
                                           '{\\bcancel{2}\\times 12}\]'
                                           '\[x=-\\frac{1}{12}\]')
Пример #8
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def rubbish_polynomial():
    return Polynomial([
        Monomial(('+', 1, 2)),
        Monomial(('+', 7, 1)),
        Monomial(('-', 10, 2)),
        Monomial(('-', 9, 1)),
        Monomial(('+', 9, 2))
    ])
Пример #9
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def test_complicated_sum_02():
    """Is this Sum correctly printed as (6+x)^{2}+12(2+11x)?"""
    assert Sum([
        BinomialIdentity((Monomial(('+', 6, 0)), Monomial(('+', 1, 1)))),
        Expandable(
            (Monomial(('+', 12, 0)),
             Sum([Polynomial([Monomial(('+', 2, 0)),
                              Monomial(('+', 11, 1))])])))
    ]).printed == wrap_nb('(6+x)^{2}+12(2+11x)')
Пример #10
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def test_eq0_autoresolution():
    """Is this Equation correctly auto-resolved?"""
    eq = Equation((Polynomial([Monomial(
        ('+', 1, 1)), Monomial(('+', 7, 0))]), Item(3)),
                  number=1)
    assert eq.auto_resolution() == wrap_nb('$(\\text{E}_{1}): $'
                                           '\[x+7=3\]'
                                           '\[x=3-7\]'
                                           '\[x=-4\]')
Пример #11
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def test_eq1_autoresolution():
    """Is this Equation correctly auto-resolved?"""
    eq = Equation((Polynomial([Monomial(
        ('-', 8, 0)), Monomial(('+', 1, 1))]), Item(-2)),
                  number=1)
    assert eq.auto_resolution() == wrap_nb('$(\\text{E}_{1}): $'
                                           '\[-8+x=-2\]'
                                           '\[x=-2+8\]'
                                           '\[x=6\]')
Пример #12
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def test_eq2_autoresolution():
    """Is this Equation correctly auto-resolved?"""
    eq = Equation(
        (Item(-5), Polynomial([Monomial(
            ('+', 1, 1)), Monomial(('+', 3, 0))])),
        number=1)
    assert eq.auto_resolution() == wrap_nb('$(\\text{E}_{1}): $'
                                           '\[-5=x+3\]'
                                           '\[x=-5-3\]'
                                           '\[x=-8\]')
Пример #13
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def test_eq6_autoresolution():
    """Is this Equation correctly auto-resolved?"""
    eq = Equation((Polynomial([Monomial(
        ('+', 2, 1)), Monomial(('+', 3, 0))]), Item(8)),
                  number=1)
    assert eq.auto_resolution() == wrap_nb('$(\\text{E}_{1}): $'
                                           '\[2x+3=8\]'
                                           '\[2x=8-3\]'
                                           '\[2x=5\]'
                                           '\[x=\\frac{5}{2}\]')
Пример #14
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def test_eq7_autoresolution():
    """Is this Equation correctly auto-resolved?"""
    eq = Equation((Polynomial([Monomial(
        ('+', 19, 0)), Monomial(('+', 3, 1))]), Monomial(('+', 2, 1))),
                  number=1)
    assert eq.auto_resolution() == wrap_nb('$(\\text{E}_{1}): $'
                                           '\[19+3x=2x\]'
                                           '\[3x-2x=-19\]'
                                           '\[(3-2)x=-19\]'
                                           '\[x=-19\]')
Пример #15
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def test_eq12_autoresolution():
    """Is this Equation correctly auto-resolved?"""
    eq = Equation((Polynomial([Monomial(
        ('+', 2, 1)), Monomial(('+', 1, 0))]), Item(1)),
                  number=1)
    assert eq.auto_resolution() == wrap_nb('$(\\text{E}_{1}): $'
                                           '\[2x+1=1\]'
                                           '\[2x=1-1\]'
                                           '\[2x=0\]'
                                           '\[x=0\]')
Пример #16
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def level_02(q_subkind, **options):

    max_coeff = 20

    if 'max_coeff' in options and is_.an_integer(options['max_coeff']):
        max_coeff = options['max_coeff']

    attribute_a_minus_sign = 'randomly'

    if 'minus_sign' in options and options['minus_sign']:
        attribute_a_minus_sign = 'yes'

    elif 'minus_sign' in options and not options['minus_sign']:
        attribute_a_minus_sign = 'no'

    # Creation of the objects

    # The three Monomials: ax², bx and c
    # Maybe we don't need to keep the integer values...
    a_val = randomly.integer(1, max_coeff)
    b_val = randomly.integer(1, max_coeff)
    c_val = randomly.integer(1, max_coeff)

    if q_subkind in [
            'type_1_A0', 'type_1_B0', 'type_1_C0', 'type_1_A1', 'type_1_B1',
            'type_1_C1'
    ]:
        # __
        c_val = randomly.integer(2, max_coeff)

    ax2 = Monomial((randomly.sign(), a_val, 2))
    bx = Monomial((randomly.sign(), b_val, 1))
    c = Monomial((randomly.sign(), c_val, 0))

    # deg1: mx + p
    # and we need two of them
    deg1 = []
    for i in range(2):
        deg1_mx = Monomial((randomly.sign(), randomly.integer(1,
                                                              max_coeff), 1))
        deg1_p = None

        if q_subkind in [
                'type_1_A0', 'type_1_B0', 'type_1_C0', 'type_1_D0',
                'type_1_E0', 'type_1_F0', 'type_1_G0', 'type_1_H0',
                'type_1_I0', 'type_1_A1', 'type_1_B1', 'type_1_D1',
                'type_1_E1', 'type_1_G1', 'type_1_H1', 'type_4_A0'
        ]:
            # __
            deg1_p = Monomial(
                (randomly.sign(), randomly.integer(1, max_coeff), 0))
        else:
            deg1_p = Monomial(
                (randomly.sign(), randomly.integer(0, max_coeff), 0))

        if not deg1_p.is_null():
            lil_box = [deg1_mx, deg1_p]
            deg1.append(
                Polynomial([randomly.pop(lil_box),
                            randomly.pop(lil_box)]))

        else:
            deg1.append(deg1_mx)

    # deg2: mx² + px + r
    # and we also need two of them
    deg2 = []
    for i in range(2):
        deg2_mx2 = Monomial((randomly.sign(), randomly.integer(1,
                                                               max_coeff), 2))

        deg2_px = None
        deg2_r = None

        if q_subkind in [
                'type_1_A0', 'type_1_B0', 'type_1_C0', 'type_1_D0',
                'type_1_E0', 'type_1_F0', 'type_1_G0', 'type_1_H0',
                'type_1_I0', 'type_1_A1', 'type_1_B1', 'type_1_D1',
                'type_1_E1', 'type_1_G1', 'type_1_H1'
        ]:
            # __
            if randomly.heads_or_tails():
                deg2_px = Monomial(
                    (randomly.sign(), randomly.integer(1, max_coeff), 1))
                deg2_r = Monomial(
                    (randomly.sign(), randomly.integer(0, max_coeff), 0))
            else:
                deg2_px = Monomial(
                    (randomly.sign(), randomly.integer(0, max_coeff), 1))
                deg2_r = Monomial(
                    (randomly.sign(), randomly.integer(1, max_coeff), 0))
        else:
            deg2_px = Monomial(
                (randomly.sign(), randomly.integer(0, max_coeff), 1))
            deg2_r = Monomial(
                (randomly.sign(), randomly.integer(0, max_coeff), 0))

        lil_box = [deg2_mx2]

        if not deg2_px.is_null():
            lil_box.append(deg2_px)
        if not deg2_r.is_null():
            lil_box.append(deg2_r)

        monomials_list_for_deg2 = []
        for i in range(len(lil_box)):
            monomials_list_for_deg2.append(randomly.pop(lil_box))

        deg2.append(Polynomial(monomials_list_for_deg2))

    # Let's attribute the common factor C according to the required type
    # (NB: expression ± C×F1 ± C×F2)
    C = None

    if q_subkind in [
            'type_1_A0', 'type_1_B0', 'type_1_C0', 'type_1_A1', 'type_1_B1'
    ]:
        # __
        C = c

    elif q_subkind in [
            'type_1_D0', 'type_1_E0', 'type_1_F0', 'type_1_D1', 'type_1_E1'
    ]:
        # __
        C = bx

    elif q_subkind in [
            'type_1_G0', 'type_1_H0', 'type_1_I0', 'type_1_G1', 'type_1_H1'
    ]:
        # __
        C = ax2

    elif q_subkind in [
            'type_2_A0', 'type_2_B0', 'type_2_C0', 'type_2_A1', 'type_2_B1',
            'type_4_A0'
    ]:
        # __
        C = Polynomial([bx, c])

    elif q_subkind in [
            'type_2_D0', 'type_2_E0', 'type_2_F0', 'type_2_D1', 'type_2_E1'
    ]:
        # __
        C = Polynomial([ax2, c])

    elif q_subkind in [
            'type_3_A0', 'type_3_B0', 'type_3_C0', 'type_3_A1', 'type_3_B1'
    ]:
        # __
        C = Polynomial([ax2, bx, c])

    # Let's attribute F1 and F2 according to the required type
    # (NB: expression ± C×F1 ± C×F2)
    F1 = None
    F2 = None

    if q_subkind in [
            'type_1_A0', 'type_1_A1', 'type_1_D0', 'type_1_D1', 'type_1_G0',
            'type_1_G1', 'type_2_A0', 'type_2_A1', 'type_2_D0', 'type_2_D1',
            'type_3_A0', 'type_3_A1'
    ]:
        # __
        F1 = deg1[0]
        F2 = deg1[1]

    elif q_subkind in [
            'type_1_B0', 'type_1_B1', 'type_1_E0', 'type_1_E1', 'type_1_H0',
            'type_1_H1', 'type_2_B0', 'type_2_B1', 'type_2_E0', 'type_2_E1',
            'type_3_B0', 'type_3_B1'
    ]:
        # __
        F1 = deg2[0]
        F2 = deg2[1]

    elif q_subkind in [
            'type_1_C0', 'type_1_F0', 'type_1_I0', 'type_2_C0', 'type_2_F0',
            'type_3_C0'
    ]:
        # __
        F1 = deg1[0]
        F2 = deg2[0]

    # The special case type_4_A0: (ax+b)² + (ax+b)×deg1'
    #                       aka    C² + C×F1
    elif q_subkind == 'type_4_A0':
        F1 = C.clone()
        F2 = deg1[0]

    # Let's put a "1" somewhere in the type_*_*1
    if q_subkind in [
            'type_1_A1', 'type_1_D1', 'type_1_G1', 'type_2_A1', 'type_2_D1',
            'type_3_A1', 'type_1_B1', 'type_1_E1'
            'type_1_H1', 'type_2_B1', 'type_2_E1', 'type_3_B1'
    ]:
        # __
        if randomly.heads_or_tails():
            F1 = Item(1)
        else:
            F2 = Item(1)

    # Let's possibly attribute a minus_sign
    # (NB: expression ± C×F1 ± C×F2)
    minus_sign = None
    # this will contain the name of the factor having
    # a supplementary minus sign in such cases:
    # C×F1 - C×F2# - C×F1 + C×F2

    # in all the following cases, it doesn't bring anything to attribute
    # a minus sign
    if ((q_subkind
         in ['type_1_A0', 'type_1_B0', 'type_1_C0', 'type_1_A1', 'type_1_B1']
         and c_val < 0) or
        ((q_subkind
          in ['type_1_D0', 'type_1_E0', 'type_1_F0', 'type_1_D1', 'type_1_E1'])
         and b_val < 0) or
        ((q_subkind
          in ['type_1_G0', 'type_1_H0', 'type_1_I0', 'type_1_G1', 'type_1_H1'])
         and a_val < 0)):
        # __
        pass  # here we let minus_sign equal to None

    # otherwise, let's attribute one randomly,
    # depending on attribute_a_minus_sign
    else:
        if attribute_a_minus_sign in ['yes', 'randomly']:
            # __
            if (attribute_a_minus_sign == 'yes' or randomly.heads_or_tails()):
                # __
                if randomly.heads_or_tails():
                    minus_sign = "F1"
                else:
                    minus_sign = "F2"
            else:
                pass  # here we let minus_sign equal to None

    # Now let's build the expression !
    expression = None
    box_product1 = [C, F1]
    box_product2 = [C, F2]

    if q_subkind == 'type_4_A0':
        CF1 = Product([C])
        CF1.set_exponent(Value(2))
    else:
        CF1 = Product([randomly.pop(box_product1), randomly.pop(box_product1)])

    CF2 = Product([randomly.pop(box_product2), randomly.pop(box_product2)])

    if minus_sign == "F1":
        if len(F1) >= 2:
            CF1 = Expandable((Item(-1), CF1))
        else:
            CF1 = Product([Item(-1), CF1])

    elif minus_sign == "F2":
        if len(F2) >= 2:
            CF2 = Expandable((Item(-1), CF2))
        else:
            CF2 = Product([Item(-1), CF2])

    expression = Sum([CF1, CF2])

    # Now let's build the factorization steps !
    steps = []
    steps.append(expression)

    F1F2_sum = None

    if minus_sign is None:
        F1F2_sum = Sum([F1, F2])

    elif minus_sign == "F1":
        if len(F1) >= 2:
            F1F2_sum = Sum([Expandable((Item(-1), F1)), F2])
        else:
            F1F2_sum = Sum([Product([Item(-1), F1]), F2])

    elif minus_sign == "F2":
        if len(F2) >= 2:
            F1F2_sum = Sum([F1, Expandable((Item(-1), F2))])
        else:
            F1F2_sum = Sum([F1, Product([Item(-1), F2])])

    temp = Product([C, F1F2_sum])
    temp.set_compact_display(False)
    steps.append(temp)

    F1F2_sum = F1F2_sum.expand_and_reduce_next_step()

    while F1F2_sum is not None:
        steps.append(Product([C, F1F2_sum]))
        F1F2_sum = F1F2_sum.expand_and_reduce_next_step()

    # This doesn't fit the need, because too much Products are
    # wrongly recognized as reducible !
    if steps[len(steps) - 1].is_reducible():
        steps.append(steps[len(steps) - 1].reduce_())

    return steps
Пример #17
0
def level_03(q_subkind, **options):

    a = randomly.integer(1, 10)
    b = randomly.integer(1, 10)

    steps = []

    if q_subkind in [
            'sum_square', 'sum_square_mixed', 'difference_square',
            'difference_square_mixed'
    ]:
        # __
        first_term = Monomial(('+', Item(('+', a, 2)).evaluate(), 2))

        second_term = Monomial(
            ('+', Item(('+', Product([2, a, b]).evaluate(), 1)).evaluate(), 1))

        third_term = Monomial(('+', Item(('+', b, 2)).evaluate(), 0))

        if q_subkind in ['difference_square', 'difference_square_mixed']:
            second_term.set_sign('-')

        if q_subkind in ['sum_square_mixed', 'difference_square_mixed']:
            ordered_expression = Polynomial(
                [first_term, second_term, third_term])

            [first_term, second_term,
             third_term] = randomly.mix([first_term, second_term, third_term])

        steps.append(Polynomial([first_term, second_term, third_term]))

        if q_subkind in ['sum_square_mixed', 'difference_square_mixed']:
            steps.append(ordered_expression)

        sq_a_monom = Monomial(('+', a, 1))
        sq_b_monom = Monomial(('+', b, 0))

        let_a_eq = Equality([Item('a'), sq_a_monom])

        let_b_eq = Equality([Item('b'), sq_b_monom])

        steps.append(
            _("Let") + " " + let_a_eq.into_str(force_expression_markers=True) +
            " " + _("and") + " " +
            let_b_eq.into_str(force_expression_markers=True))

        sq_a_monom.set_exponent(2)
        sq_b_monom.set_exponent(2)

        a_square_eq = Equality(
            [Item(('+', 'a', 2)), sq_a_monom,
             sq_a_monom.reduce_()])

        b_square_eq = Equality(
            [Item(('+', 'b', 2)), sq_b_monom,
             sq_b_monom.reduce_()])

        steps.append(
            _("then") + " " +
            a_square_eq.into_str(force_expression_markers=True))

        steps.append(
            _("and") + " " +
            b_square_eq.into_str(force_expression_markers=True))

        two_times_a_times_b_numeric = Product(
            [Item(2), Monomial(('+', a, 1)),
             Item(b)])

        two_times_a_times_b_reduced = two_times_a_times_b_numeric.reduce_()

        two_times_a_times_b_eq = Equality([
            Product([Item(2), Item('a'), Item('b')]),
            two_times_a_times_b_numeric, two_times_a_times_b_reduced
        ])

        steps.append(
            _("and") + " " +
            two_times_a_times_b_eq.into_str(force_expression_markers=True))

        steps.append(_("So it is possible to factorize:"))

        if q_subkind in ['difference_square', 'difference_square_mixed']:
            b = -b

        factorized_expression = Sum([Monomial(('+', a, 1)), Item(b)])
        factorized_expression.set_exponent(2)

        steps.append(factorized_expression)

    elif q_subkind in ['squares_difference', 'squares_difference_mixed']:
        # To have some (ax)² - b² but also sometimes b² - (ax)²:
        degrees = [2, 0, 1, 0]

        if randomly.integer(1, 10) >= 8:
            degrees = [0, 2, 0, 1]

        first_term = Monomial(('+', Item(('+', a, 2)).evaluate(), degrees[0]))

        second_term = Monomial(('-', Item(('+', b, 2)).evaluate(), degrees[1]))

        sq_first_term = Monomial(('+', Item(
            ('+', a, 1)).evaluate(), degrees[2]))

        sq_second_term = Monomial(('-', Item(
            ('+', b, 1)).evaluate(), degrees[3]))

        # The 'mixed' cases are: -b² + (ax)² and -(ax)² + b²
        if q_subkind == 'squares_difference_mixed':
            [first_term, second_term] = randomly.mix([first_term, second_term])
            [sq_first_term,
             sq_second_term] = randomly.mix([sq_first_term, sq_second_term])

        positive_sq_first = sq_first_term.clone()
        positive_sq_first.set_sign('+')
        positive_sq_second = sq_second_term.clone()
        positive_sq_second.set_sign('+')

        steps.append(Polynomial([first_term, second_term]))

        first_inter = None
        second_inter = None

        if sq_second_term.is_negative():
            first_inter = positive_sq_first.clone()
            first_inter.set_exponent(2)
            temp_second_inter = positive_sq_second.clone()
            temp_second_inter.set_exponent(2)
            second_inter = Product([-1, temp_second_inter])
        else:
            temp_first_inter = positive_sq_first.clone()
            temp_first_inter.set_exponent(2)
            first_inter = Product([-1, temp_first_inter])
            second_inter = positive_sq_second.clone()
            second_inter.set_exponent(2)

        steps.append(Sum([first_inter, second_inter]))

        if q_subkind == 'squares_difference_mixed':
            steps.append(Sum([second_inter, first_inter]))

        steps.append(_("So, this expression can be factorized:"))

        sum1 = None
        sum2 = None

        if sq_second_term.is_negative():
            sum1 = Sum([sq_first_term, sq_second_term])
            sq_second_term.set_sign('+')
            sum2 = Sum([sq_first_term, sq_second_term])

        else:
            sum1 = Sum([sq_second_term, sq_first_term])
            sq_first_term.set_sign('+')
            sum2 = Sum([sq_second_term, sq_first_term])

        lil_box = [sum1, sum2]

        steps.append(Product([randomly.pop(lil_box), randomly.pop(lil_box)]))

    elif q_subkind in [
            'fake_01', 'fake_01_mixed', 'fake_02', 'fake_02_mixed', 'fake_03',
            'fake_03_mixed', 'fake_04_A', 'fake_04_A_mixed', 'fake_04_B',
            'fake_04_B_mixed', 'fake_04_C', 'fake_04_C_mixed', 'fake_04_D',
            'fake_04_D_mixed'
    ]:
        # __
        straight_cases = [
            'fake_01', 'fake_02', 'fake_03', 'fake_04_A', 'fake_04_B',
            'fake_04_C', 'fake_04_D'
        ]
        match_pb_cases = [
            'fake_01', 'fake_02', 'fake_01_mixed', 'fake_02_mixed'
        ]
        sign_pb_cases = [
            'fake_03', 'fake_03_mixed', 'fake_04_A', 'fake_04_B', 'fake_04_C',
            'fake_04_D', 'fake_04_A_mixed', 'fake_04_B_mixed',
            'fake_04_C_mixed', 'fake_04_D_mixed'
        ]

        ax = Monomial(('+', a, 1))
        b_ = Monomial(('+', b, 0))

        ax_2 = ax.clone()
        ax_2.set_exponent(2)
        a2x2 = Monomial(('+', a * a, 2))

        b_2 = Monomial(('+', b, 0))
        b_2.set_exponent(2)

        b2 = Monomial(('+', b * b, 0))

        two_ax_b = Product([Item(2), Monomial(('+', a, 1)), Item(b)])

        twoabx = Monomial(('+', 2 * a * b, 1))

        fake_twoabx = Monomial(('+', a * b, 1))

        if randomly.integer(1, 10) >= 8:
            fake_twoabx = Monomial(
                ('+',
                 2 * a * b + randomly.pop([-1, 1]) * randomly.integer(1, 5),
                 1))
        first_term = None
        second_term = None
        third_term = None

        ordered_expression = None
        mixed_expression = None

        if q_subkind == 'fake_03' or q_subkind == 'fake_03_mixed':
            first_term = a2x2.clone()
            second_term = b2.clone()
            ordered_expression = Polynomial([first_term, second_term])
            mixed_expression = Polynomial([second_term, first_term])

        else:
            first_term = a2x2.clone()
            third_term = b2.clone()

            if q_subkind in [
                    'fake_01', 'fake_01_mixed', 'fake_02', 'fake_02_mixed'
            ]:
                # __
                second_term = fake_twoabx.clone()

            else:
                second_term = twoabx.clone()

            if q_subkind == 'fake_02' or q_subkind == 'fake_02_mixed':
                second_term.set_sign('-')

            elif q_subkind == 'fake_04_A' or q_subkind == 'fake_04_A_mixed':
                third_term.set_sign('-')

            elif q_subkind == 'fake_04_B' or q_subkind == 'fake_04_B_mixed':
                first_term.set_sign('-')

            elif q_subkind == 'fake_04_C' or q_subkind == 'fake_04_C_mixed':
                second_term.set_sign('-')
                third_term.set_sign('-')

            elif q_subkind == 'fake_04_D' or q_subkind == 'fake_04_D_mixed':
                first_term.set_sign('-')
                second_term.set_sign('-')

            ordered_expression = Polynomial(
                [first_term, second_term, third_term])

            mixed_expression = Polynomial(
                randomly.mix([first_term, second_term, third_term]))
        if q_subkind in straight_cases:
            steps.append(ordered_expression)

        elif q_subkind == 'fake_03_mixed':
            steps.append(mixed_expression)

        else:
            steps.append(mixed_expression)
            steps.append(ordered_expression)

        if q_subkind in match_pb_cases:
            let_a_eq = Equality([Item('a'), ax])

            let_b_eq = Equality([Item('b'), b_])

            steps.append(
                _("Let") + " " +
                let_a_eq.into_str(force_expression_markers=True) + " " +
                _("and") + " " +
                let_b_eq.into_str(force_expression_markers=True))

            a_square_eq = Equality([Item(('+', 'a', 2)), ax_2, a2x2])

            b_square_eq = Equality([Item(('+', 'b', 2)), b_2, b2])

            steps.append(
                _("then") + " " +
                a_square_eq.into_str(force_expression_markers=True))

            steps.append(
                _("and") + " " +
                b_square_eq.into_str(force_expression_markers=True))

            two_times_a_times_b_eq = Equality([
                Product([Item(2), Item('a'), Item('b')]), two_ax_b, twoabx,
                fake_twoabx
            ],
                                              equal_signs=['=', '=', 'neq'])

            steps.append(
                _("but") + " " +
                two_times_a_times_b_eq.into_str(force_expression_markers=True))

            steps.append(_("So it does not match a binomial identity."))
            steps.append(_("This expression cannot be factorized."))

        elif q_subkind in sign_pb_cases:
            steps.append(_("Because of the signs,"))
            steps.append(_("it does not match a binomial identity."))
            steps.append(_("This expression cannot be factorized."))

    return steps
Пример #18
0
def test_complicated_sum_01():
    """Is this Sum correctly printed as 2-10x^{2}+9?"""
    assert Sum([Item(2),
                Product([Polynomial([Monomial(('-', 10, 2)),
                                     Monomial(('+', 9, 0))])])]).printed == \
        wrap_nb('2-10x^{2}+9')
    def __init__(self, q_kind='default_nothing', **options):
        self.derived = True

        # The call to the mother class __init__() method will set the
        # fields matching optional arguments which are so far:
        # self.q_kind, self.q_subkind
        # plus self.options (modified)
        Q_Structure.__init__(self, q_kind, AVAILABLE_Q_KIND_VALUES, **options)
        # The purpose of this next line is to get the possibly modified
        # value of **options
        options = self.options

        MAX_COEFF = MAX_COEFF_TABLE[q_kind]
        MAX_EXPONENT = MAX_EXPONENT_TABLE[q_kind]
        DEFAULT_MINIMUM_LENGTH = DEFAULT_MINIMUM_LENGTH_TABLE[q_kind]
        DEFAULT_MAXIMUM_LENGTH = DEFAULT_MAXIMUM_LENGTH_TABLE[q_kind]

        # This field is to be used in the answer_to_strs() method
        # to determine a possibly different algorithm for particular cases
        self.kind_of_answer = ""

        # Max coefficient & degree values...
        max_coeff = MAX_COEFF
        max_expon = MAX_EXPONENT

        if 'max_coeff' in options and options['max_coeff'] >= 1:
            max_coeff = options['max_coeff']

        if 'max_expon' in options and options['max_expon'] >= 1:
            max_expon = options['max_expon']

        length = randomly.integer(DEFAULT_MINIMUM_LENGTH,
                                  DEFAULT_MAXIMUM_LENGTH,
                                  weighted_table=[0.15, 0.25, 0.6])

        if ('length' in options and is_.an_integer(options['length'])
                and options['length'] >= 2):
            # __
            length = options['length']

        # 1st CASE:
        # PRODUCT REDUCTION
        if q_kind == 'product':
            # First let's determine a pack of letters where to draw
            # The default one will be [a, b, c, x, y, z]
            # but the reduced or entire alphabets can be used as well
            letters_package = alphabet.abc + alphabet.xyz

            if 'short_test' in options and options['short_test']:
                # __
                self.objct = Product(
                    [Monomial((RANDOMLY, 12, 1)),
                     Monomial((RANDOMLY, 12, 1))])

                self.objct.factor[0].set_degree(1)
                self.objct.factor[1].set_degree(1)

            else:
                # In the case of an exercise about reducing products
                # in a training sheet, the answers will be more detailed
                self.kind_of_answer = 'product_detailed'
                if 'use_reduced_alphabet' in options:
                    letters_package = alphabet.reduced

                elif 'use_the_entire_alphabet' in options:
                    letters_package = alphabet.lowercase

                elif 'use_these_letters' in options                           \
                     and is_.a_string_list(options['use_these_letters']):
                    # __
                    letters_package = options['use_these_letters']

                # Maximum Items number. (We make sure at the same time that
                # we won't
                # risk to draw a greater number of letters than the available
                # letters
                # in letters_package)
                max_literal_items_nb = min(PR_MAX_LITERAL_ITEMS_NB,
                                           len(letters_package))

                if ('max_literal_items_nb' in options
                        and 2 <= options['max_literal_items_nb'] <= 6):
                    # __
                    max_literal_items_nb = min(options['max_literal_items_nb'],
                                               len(letters_package))

                # Maximum number of occurences of the same letter in
                # the initial expression
                same_letter_max_occurences = PR_SAME_LETTER_MAX_OCCURENCES_NB

                if ('nb_occurences_of_the_same_letter' in options
                        and options['nb_occurences_of_the_same_letter'] >= 1):
                    # __
                    same_letter_max_occurences = options['nb_occurences_of'
                                                         '_the_same_letter']

                # CREATION OF THE EXPRESSION
                # We draw randomly the letters that will appear
                # in the expression
                current_letters_package = list(letters_package)

                nb_of_letters_to_draw = randomly.integer(
                    1, max_literal_items_nb)

                drawn_letters = list()

                for j in range(nb_of_letters_to_draw):
                    drawn_letters.append(randomly.pop(current_letters_package))

                # Let's determine how many times will appear each letter
                # and then create a list containing each of these letters
                # the number of times they will appear
                pre_items_list = list()
                items_list = list()

                for j in range(len(drawn_letters)):
                    if j == 0:
                        # We make sure that at least one letter occurs twice
                        # so that the exercise remains interesting !
                        # But the number of cases this letter occurs 3 three
                        # times  should be limited to keep sufficient
                        # simple cases for the pupils to begin with.
                        # It is really easy to make it much more complicated
                        # simply giving:
                        # nb_occurences_of_the_same_letter=<enough_high_nb>
                        # as an argument.
                        if randomly.decimal_0_1() < 0.5:
                            occurences_nb = 2
                        else:
                            occurences_nb = randomly\
                                .integer(2, same_letter_max_occurences)
                    else:
                        occurences_nb = randomly\
                            .integer(1, same_letter_max_occurences)

                    if occurences_nb >= 1:
                        for k in range(occurences_nb):
                            pre_items_list.append(drawn_letters[j])

                # draw the number of numeric Items
                nb_item_num = randomly.integer(1, PR_NUMERIC_ITEMS_MAX_NB)

                # put them in the pre items' list
                for j in range(nb_item_num):
                    pre_items_list.append(NUMERIC)

                # prepare the items' list that will be given to the Product's
                # constructor
                loop_nb = len(pre_items_list)

                for j in range(loop_nb):
                    next_item_kind = randomly.pop(pre_items_list)

                    # It's not really useful nor really possible to limit the
                    # number
                    # of occurences of the same letter being drawn twice in
                    # a row because it belongs to the exercise and there
                    # are many cases when
                    # the same letter is in the list in 3 over 4 elements.
                    # if j >= 1 and next_item_kind == items_list[j - 1]
                    # .raw_value:
                    #    pre_items_list.append(next_item_kind)
                    #    next_item_kind = randomly.pop(pre_items_list)

                    if next_item_kind == NUMERIC:
                        temp_item = Item((randomly.sign(plus_signs_ratio=0.75),
                                          randomly.integer(1, max_coeff), 1))
                        items_list.append(temp_item)

                    else:
                        item_value = next_item_kind
                        temp_item = Item(
                            (randomly.sign(plus_signs_ratio=0.9), item_value,
                             randomly.integer(1, max_expon)))
                        items_list.append(temp_item)

                # so now that the items_list is complete,
                # let's build the Product !
                self.objct = Product(items_list)
                self.objct.set_compact_display(False)

                # Let's take some × symbols off the Product to match a more
                # usual situation
                for i in range(len(self.objct) - 1):
                    if ((self.objct.factor[i].is_numeric()
                         and self.objct.factor[i + 1].is_literal())
                            or (self.objct.factor[i].is_literal()
                                and self.objct.factor[i + 1].is_literal()
                                and self.objct.factor[i].raw_value !=
                                self.objct.factor[i + 1].raw_value
                                and randomly.decimal_0_1() > 0.5)):
                        # __
                        self.objct.info[i] = False

        # 2d CASE:
        # SUM OF PRODUCTS REDUCTION
        if q_kind == 'sum_of_products':
            if (not ('length' in options and is_.an_integer(options['length'])
                     and options['length'] >= 2)):
                # __
                length = randomly.integer(DEFAULT_MINIMUM_LENGTH,
                                          DEFAULT_MAXIMUM_LENGTH,
                                          weighted_table=[0.15, 0.25, 0.6])

            # Creation of the list to give later to the Sum constructor
            products_list = list()

            for i in range(length):
                monomial1 = Monomial((RANDOMLY, max_coeff, max_expon))
                monomial2 = Monomial((RANDOMLY, max_coeff, max_expon))
                products_list.append(Product([monomial1, monomial2]))

            # Creation of the Sum
            self.objct = Sum(products_list)

        # 3d CASE:
        # SUM REDUCTION
        if q_kind == 'sum':
            self.kind_of_answer = 'sum'
            # Let's determine the length of the Sum to create
            if not ('length' in options and is_.an_integer(options['length'])
                    and options['length'] >= 1):
                # __
                length = randomly\
                    .integer(DEFAULT_MINIMUM_LENGTH,
                             DEFAULT_MAXIMUM_LENGTH,
                             weighted_table=[0.1, 0.25, 0.5, 0.1, 0.05])

            else:
                length = options['length']

            # Creation of the Polynomial...

            if 'short_test' in options:
                self.objct = Polynomial((RANDOMLY, max_coeff, 2, length - 1))
                temp_sum = self.objct.term

                degree_1_monomial_here = False
                for i in range(len(temp_sum)):
                    if temp_sum[i].degree == 1:
                        degree_1_monomial_here = True

                if degree_1_monomial_here == 1:
                    temp_sum.append(Monomial((randomly.sign(), 1, 1)))
                else:
                    # this should be 2d deg Polynomial w/out any 1st deg term
                    temp_sum.append(Monomial((randomly.sign(), 1, 2)))

                self.objct.reset_element()

                for i in range(length):
                    self.objct.term.append(randomly.pop(temp_sum))
                    self.objct.info.append(False)

            else:
                self.objct = Polynomial(
                    (RANDOMLY, max_coeff, max_expon, length))

        if q_kind == 'long_sum':
            m = []

            for i in range(length):
                m.append(Monomial(RANDOMLY, max_coeff, max_expon))

            self.objct = Polynomial(m)

        if q_kind == 'long_sum_including_a_coeff_1':
            m = []

            for i in range(length - 1):
                m.append(Monomial(RANDOMLY, max_coeff, max_expon))

            m.append(Monomial(RANDOMLY, 1, max_expon))

            terms_list = []

            for i in range(len(m)):
                terms_list.append(randomly.pop(m))

            self.objct = Polynomial(terms_list)

        if q_kind == 'sum_not_reducible':
            self.kind_of_answer = 'sum_not_reducible'

            m1 = Monomial((RANDOMLY, max_coeff, 0))
            m2 = Monomial((RANDOMLY, max_coeff, 1))
            m3 = Monomial((RANDOMLY, max_coeff, 2))

            lil_box = [m1, m2, m3]

            self.objct = Polynomial([randomly.pop(lil_box)])

            for i in range(len(lil_box) - 1):
                self.objct.append(randomly.pop(lil_box))

        if q_kind == 'sum_with_minus-brackets':
            minus_brackets = []

            for i in range(3):
                minus_brackets.append(
                    Expandable((Monomial(('-', 1, 0)),
                                Polynomial(
                                    (RANDOMLY, 15, 2, randomly.integer(2,
                                                                       3))))))
            m1 = Monomial((RANDOMLY, max_coeff, 0))
            m2 = Monomial((RANDOMLY, max_coeff, 1))
            m3 = Monomial((RANDOMLY, max_coeff, 2))
            m4 = Monomial((RANDOMLY, max_coeff, randomly.integer(0, 2)))

            lil_box = [m1, m2, m3, m4]

            plus_brackets = []

            for i in range(3):
                plus_brackets.append(
                    Expandable((Monomial(('+', 1, 0)),
                                Polynomial(
                                    (RANDOMLY, 15, 2, randomly.integer(2,
                                                                       3))))))

            big_box = []
            big_box.append(minus_brackets[0])

            if ('minus_brackets_nb' in options
                    and 2 <= options['minus_brackets_nb'] <= 3):
                # __
                big_box.append(minus_brackets[1])

                if options['minus_brackets_nb'] == 3:
                    big_box.append(minus_brackets[2])

            for i in range(randomly.integer(1, 4)):
                big_box.append(randomly.pop(lil_box))

            if ('plus_brackets_nb' in options
                    and 1 <= options['plus_brackets_nb'] <= 3):
                # __
                for i in range(options['plus_brackets_nb']):
                    big_box.append(plus_brackets[i])

            final_terms = []

            for i in range(len(big_box)):
                final_terms.append(randomly.pop(big_box))

            self.objct = Sum(final_terms)

        # Creation of the expression:
        number = 0
        if ('expression_number' in options
                and is_.a_natural_int(options['expression_number'])):
            # __
            number = options['expression_number']

        self.expression = Expression(number, self.objct)
    def __init__(self, q_kind='default_nothing', **options):
        self.derived = True

        # The call to the mother class __init__() method will set the
        # fields matching optional arguments which are so far:
        # self.q_kind, self.q_subkind
        # plus self.options (modified)
        Q_Structure.__init__(self, q_kind, AVAILABLE_Q_KIND_VALUES, **options)
        # The purpose of this next line is to get the possibly modified
        # value of **options
        options = self.options

        init_caller = INIT_CALLER[q_kind]

        self.expandable_objct = None

        self.numeric_aux = None

        if q_kind == 'any_basic_expd':
            randomly_drawn = randomly.decimal_0_1()
            if randomly_drawn <= 0.25:
                self.expandable_objct = Expandable((RANDOMLY, 'monom0_polyn1'),
                                                   randomly_reversed=0.5)
            elif randomly_drawn <= 0.50:
                self.expandable_objct = Expandable((RANDOMLY, 'monom1_polyn1'),
                                                   randomly_reversed=0.5)
            else:
                self.expandable_objct = Expandable((RANDOMLY, 'polyn1_polyn1'))

        elif q_kind in ['monom0_polyn1', 'monom1_polyn1']:
            self.expandable_objct = Expandable((RANDOMLY, q_kind),
                                               randomly_reversed=0.5)
        elif q_kind == 'monom01_polyn1':
            self.expandable_objct = Expandable(
                (RANDOMLY, randomly.pop(['monom0_polyn1', 'monom1_polyn1'])),
                randomly_reversed=0.5)

        elif q_kind == 'polyn1_polyn1':
            self.expandable_objct = Expandable((RANDOMLY, 'polyn1_polyn1'))

        elif q_kind == 'sum_of_any_basic_expd':
            if self.q_subkind in ['harder', 'with_a_binomial']:
                # __
                choices = ['monom0_polyn1', 'monom1_polyn1']

                drawn_types = list()
                drawn_types.append(randomly.pop(choices))

                if self.q_subkind == 'with_a_binomial':
                    drawn_types.append('any_binomial')
                else:
                    drawn_types.append('minus_polyn1_polyn1')

                aux_expd_list = list()

                for t in drawn_types:
                    if t == 'any_binomial':
                        aux_expd_list.append(
                            BinomialIdentity((RANDOMLY, 'any'), **options))
                    else:
                        aux_expd_list.append(Expandable((RANDOMLY, t)))

                final_list = list()
                for i in range(len(aux_expd_list)):
                    final_list.append(randomly.pop(aux_expd_list))

                self.expandable_objct = Sum(final_list)

            elif self.q_subkind == 'easy':
                choices = ['monom0_polyn1', 'monom1_polyn1']

                aux_expd_list = list()
                aux_expd_list.append(
                    Expandable((RANDOMLY, randomly.pop(choices))))

                if randomly.heads_or_tails():
                    aux_expd_list.append(Expandable((RANDOMLY, 'sign_exp')))
                else:
                    aux_expd_list.append(
                        Monomial((RANDOMLY, 15, randomly.integer(0, 2))))

                final_list = list()
                for i in range(len(aux_expd_list)):
                    final_list.append(randomly.pop(aux_expd_list))

                self.expandable_objct = Sum(final_list)

            else:
                choices = [
                    'monom0_polyn1', 'monom0_polyn1', 'monom1_polyn1',
                    'monom1_polyn1', 'polyn1_polyn1', 'minus_polyn1_polyn1'
                ]

                drawn_types = list()
                drawn_types.append(randomly.pop(choices))
                drawn_types.append(randomly.pop(choices))

                aux_expd_list = list()

                for element in drawn_types:
                    aux_expd_list.append(Expandable((RANDOMLY, element)))

                aux_expd_list.append(Monomial((RANDOMLY, 15, 2)))

                final_list = list()
                for i in range(len(aux_expd_list)):
                    final_list.append(randomly.pop(aux_expd_list))

                self.expandable_objct = Sum(final_list)

        elif q_kind in ['sign_expansion', 'sign_expansion_short_test']:
            sign_exp_kind = options.get('sign_exp_kind', 0)

            if q_kind == 'sign_expansion_short_test':
                sign_exp_kind = 1

            if sign_exp_kind == 0:
                sign_exp_kind = randomly.integer(1, 5)

            # Creation of the terms
            aux_terms_list = list()

            aux_expd_1 = Expandable((Monomial(
                (randomly.sign(), 1, 0)), Polynomial((RANDOMLY, 15, 2, 2))))

            aux_expd_2 = Expandable((Monomial(
                (randomly.sign(), 1, 0)), Polynomial((RANDOMLY, 15, 2, 2))))

            aux_expd_3 = Expandable((Monomial(
                (randomly.sign(), 1, 0)), Polynomial((RANDOMLY, 15, 2, 2))))

            long_aux_expd = Expandable((Monomial(
                (randomly.sign(), 1, 0)), Polynomial((RANDOMLY, 15, 2, 3))))

            if q_kind == 'sign_expansion_short_test':
                long_aux_expd = Expandable((Monomial(
                    ('-', 1, 0)), Polynomial((RANDOMLY, 15, 2, 3))))

            aux_monomial = Monomial((RANDOMLY, 15, 2))

            # 1st kind: a Monomial and ± (long Polynomial)
            # (like in a short test)
            if sign_exp_kind == 1:
                aux_terms_list.append(long_aux_expd)
                aux_terms_list.append(aux_monomial)

            # 2d kind: ± (x+3) ± (4x - 7)
            elif sign_exp_kind == 2:
                aux_terms_list.append(aux_expd_1)
                aux_terms_list.append(aux_expd_2)

            # 3d kind: ± (x+3) ± (4x - 7) ± (x² - 5x)
            elif sign_exp_kind == 3:
                aux_terms_list.append(aux_expd_1)
                aux_terms_list.append(aux_expd_2)
                aux_terms_list.append(aux_expd_3)

            # 4th kind: ± (x+3) ± (4x - 7) ± Monomial
            elif sign_exp_kind == 4:
                aux_terms_list.append(aux_expd_1)
                aux_terms_list.append(aux_expd_2)
                aux_terms_list.append(aux_monomial)

            # 5th kind: ± (x+3) ± Monomial ± (long Polynomial)
            elif sign_exp_kind == 5:
                aux_terms_list.append(aux_expd_2)
                aux_terms_list.append(aux_monomial)
                aux_terms_list.append(long_aux_expd)

            # add as many possibilities as wanted,
            # don't forget to increase the last number here:
            # sign_exp_kind = randomly.integer(1, 5) (what's a bit above)

            # Now let's distribute the terms randomly
            final_terms_list = list()
            for i in range(len(aux_terms_list)):
                final_terms_list.append(randomly.pop(aux_terms_list))

            self.expandable_objct = Sum(final_terms_list)

        elif q_kind in [
                'numeric_sum_square', 'numeric_difference_square',
                'numeric_squares_difference'
        ]:
            # __
            self.expandable_objct = init_caller(
                (options['couple'][0], options['couple'][1]), **options)
            if q_kind in ['numeric_sum_square', 'numeric_difference_square']:
                self.numeric_aux = Sum(
                    [options['couple'][0], options['couple'][1]]).reduce_()
                self.numeric_aux.set_exponent(2)

            else:  # squares_difference's case
                aux1 = Sum([options['couple'][0],
                            options['couple'][1]]).reduce_()
                temp = options['couple'][1].clone()
                temp.set_sign('-')
                aux2 = Sum([options['couple'][0], temp]).reduce_()
                self.numeric_aux = Product([aux1, aux2])

        else:
            if q_kind == 'any_binomial':
                q_kind = 'any'

            self.expandable_objct = init_caller((RANDOMLY, q_kind), **options)

        # Creation of the expression:
        number = 0
        if 'expression_number' in options                                     \
           and is_.a_natural_int(options['expression_number']):
            # __
            number = options['expression_number']
        self.expression = Expression(number, self.expandable_objct)
        if self.numeric_aux is not None:
            self.numeric_aux = Expression(number, self.numeric_aux)
class Q_AlgebraExpressionReduction(Q_Structure):

    # --------------------------------------------------------------------------
    ##
    #   @brief Constructor.
    #   @param q_kind= the kind of question desired
    #          Available values are: 'product'
    #                                 'sum'
    #                                 'sum_of_products'
    #   @param **options Options detailed below:
    #          - short_test=bool
    #                         'yes'
    #                         'OK'
    #                         any other value will be understood as 'no'
    #          - q_subkind=<string>
    #                    'minus_brackets_nb' (values: 1, 2, 3)
    #                    'plus_brackets_nb' (values: 1, 2, 3)
    #   @todo describe the different available options in this comment
    #   @return One instance of question.Q_AlgebraExpressionReduction
    def __init__(self, q_kind='default_nothing', **options):
        self.derived = True

        # The call to the mother class __init__() method will set the
        # fields matching optional arguments which are so far:
        # self.q_kind, self.q_subkind
        # plus self.options (modified)
        Q_Structure.__init__(self,
                             q_kind, AVAILABLE_Q_KIND_VALUES,
                             **options)
        # The purpose of this next line is to get the possibly modified
        # value of **options
        options = self.options

        MAX_COEFF = MAX_COEFF_TABLE[q_kind]
        MAX_EXPONENT = MAX_EXPONENT_TABLE[q_kind]
        MIN_LENGTH = DEFAULT_MINIMUM_LENGTH_TABLE[q_kind]
        MAX_LENGTH = DEFAULT_MAXIMUM_LENGTH_TABLE[q_kind]
        LENGTH_SPAN = MAX_LENGTH - MIN_LENGTH + 1

        # This field is to be used in the answer_to_strs() method
        # to determine a possibly different algorithm for particular cases
        self.kind_of_answer = ""

        # Max coefficient & degree values...
        max_coeff = options.get('max_coeff', MAX_COEFF)
        max_expon = options.get('max_expon', MAX_EXPONENT)
        length = options.get('length',
                             random.choice([n + MIN_LENGTH
                                            for n in range(LENGTH_SPAN)]))

        # 1st CASE:
        # PRODUCT REDUCTION
        if q_kind == 'product':
            # First let's determine a pack of letters where to draw
            # The default one will be [a, b, c, x, y, z]
            # but the reduced or entire alphabets can be used as well
            letters_package = ['a', 'b', 'c', 'x', 'y', 'z']

            self.kind_of_answer = 'product_detailed'
            if 'use_reduced_alphabet' in options:
                letters_package = ['a', 'b', 'c', 'd', 'g', 'h', 'k', 'p',
                                   'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
                                   'y', 'z']

            elif ('use_these_letters' in options
                  and type(options['use_these_letters']) is list
                  and all([type(elt) is str
                           for elt in options['use_these_letters']])):
                # __
                letters_package = options['use_these_letters']

            # Maximum Items number. (We make sure at the same time that
            # we won't
            # risk to draw a greater number of letters than the available
            # letters
            # in letters_package)
            max_literal_items_nb = min(PR_MAX_LITERAL_ITEMS_NB,
                                       len(letters_package))

            # Maximum number of occurences of the same letter in
            # the initial expression
            same_letter_max_occurences = PR_SAME_LETTER_MAX_OCCURENCES_NB

            if ('nb_occurences_of_the_same_letter' in options
                and options['nb_occurences_of_the_same_letter'] >= 1):
                # __
                same_letter_max_occurences = options['nb_occurences_of'
                                                     '_the_same_letter']

            # CREATION OF THE EXPRESSION
            # We draw randomly the letters that will appear
            # in the expression
            current_letters_package = list(letters_package)

            nb_of_letters_to_draw = random.randint(1, max_literal_items_nb)

            drawn_letters = list()

            for j in range(nb_of_letters_to_draw):
                drawn_letters.append(
                    random.choice(current_letters_package))

            # Let's determine how many times will appear each letter
            # and then create a list containing each of these letters
            # the number of times they will appear
            pre_items_list = list()
            items_list = list()

            for j in range(len(drawn_letters)):
                if j == 0:
                    # We make sure that at least one letter occurs twice
                    # so that the exercise remains interesting !
                    # But the number of cases this letter occurs 3 three
                    # times  should be limited to keep sufficient
                    # simple cases for the pupils to begin with.
                    # It is really easy to make it much more complicated
                    # simply giving:
                    # nb_occurences_of_the_same_letter=<enough_high_nb>
                    # as an argument.
                    if random.random() < 0.5:
                        occurences_nb = 2
                    else:
                        occurences_nb = \
                            random.randint(
                                min(2, same_letter_max_occurences),
                                same_letter_max_occurences)
                else:
                    occurences_nb = \
                        random.randint(1, same_letter_max_occurences)

                if occurences_nb >= 1:
                    for k in range(occurences_nb):
                        pre_items_list.append(drawn_letters[j])

            # draw the number of numeric Items
            nb_item_num = random.randint(1, PR_NUMERIC_ITEMS_MAX_NB)

            # put them in the pre items' list
            for j in range(nb_item_num):
                pre_items_list.append(NUMERIC)

            # prepare the items' list that will be given to the Product's
            # constructor
            loop_nb = len(pre_items_list)

            for j in range(loop_nb):
                next_item_kind = random.choice(pre_items_list)

                # It's not really useful nor really possible to limit the
                # number
                # of occurences of the same letter being drawn twice in
                # a row because it belongs to the exercise and there
                # are many cases when
                # the same letter is in the list in 3 over 4 elements.
                # if j >= 1 and next_item_kind == items_list[j - 1]
                # .raw_value:
                #    pre_items_list.append(next_item_kind)
                #    next_item_kind = random.choice(pre_items_list)

                if next_item_kind == NUMERIC:
                    temp_item = Item((random.choices(['+', '-'],
                                                     cum_weights=[0.75,
                                                                  1])[0],
                                      random.randint(1, max_coeff),
                                      1))
                    items_list.append(temp_item)

                else:
                    item_value = next_item_kind
                    temp_item = Item((random.choices(['+', '-'],
                                                     cum_weights=[0.9,
                                                                  1])[0],
                                      item_value,
                                      random.randint(1, max_expon)))
                    items_list.append(temp_item)

            # so now that the items_list is complete,
            # let's build the Product !
            self.objct = Product(items_list)
            self.objct.set_compact_display(False)

            # Let's take some × symbols off the Product to match a more
            # usual situation
            for i in range(len(self.objct) - 1):
                if ((self.objct.factor[i].is_numeric()
                     and self.objct.factor[i + 1].is_literal())
                    or (self.objct.factor[i].is_literal()
                        and self.objct.factor[i + 1].is_literal()
                        and self.objct.factor[i].raw_value
                        != self.objct.factor[i + 1].raw_value
                    and random.random() > 0.5)):
                    # __
                    self.objct.info[i] = False

        # 2d CASE:
        # SUM OF PRODUCTS REDUCTION
        if q_kind == 'sum_of_products':
            if (not ('length' in options and is_integer(options['length'])
                and options['length'] >= 2)):
                # __
                length = random.choices(
                    [n + MIN_LENGTH for n in range(LENGTH_SPAN)],
                    weights=[n for n in range(LENGTH_SPAN)])[0]

            # Creation of the list to give later to the Sum constructor
            products_list = list()

            for i in range(length):
                monomial1 = Monomial((RANDOMLY,
                                      max_coeff,
                                      max_expon))
                monomial2 = Monomial((RANDOMLY,
                                      max_coeff,
                                      max_expon))
                products_list.append(Product([monomial1, monomial2]))

            # Creation of the Sum
            self.objct = Sum(products_list)

        # 3d CASE:
        # SUM REDUCTION
        if q_kind == 'sum':
            self.kind_of_answer = 'sum'
            length = options.get('length',
                                 random.choice([n + MIN_LENGTH
                                                for n in range(LENGTH_SPAN)]))
            self.objct = Polynomial((RANDOMLY,
                                     max_coeff,
                                     max_expon,
                                     length))

        # Creation of the expression:
        number = 0
        if ('expression_number' in options
            and is_natural(options['expression_number'])):
            # __
            number = options['expression_number']

        self.expression = Expression(number, self.objct)

    # --------------------------------------------------------------------------
    ##
    #   @brief Returns the text of the question as a str
    def text_to_str(self):
        M = shared.machine

        result = M.write_math_style2(M.type_string(self.expression))
        result += M.write_new_line()

        return result

    # --------------------------------------------------------------------------
    ##
    #   @brief Returns the answer of the question as a str
    def answer_to_str(self):
        M = shared.machine

        result = ""

        if self.kind_of_answer == 'product_detailed':
            result += M.write_math_style2(M.type_string(self.expression))
            result += M.write_new_line()

            if not all(self.objct.factor[i]
                       .alphabetical_order_cmp(self.objct.factor[i + 1]) > 0
                       for i in range(len(self.objct.factor) - 1)):
                ordered_product = self.objct.order()
                ordered_product.set_compact_display(False)
                ordered_expression = Expression(self.expression.name,
                                                ordered_product)
                result += M.write_math_style2(
                    M.type_string(ordered_expression))
                result += M.write_new_line()

            final_product = self.objct.reduce_()
            final_expression = Expression(self.expression.name,
                                          final_product)

            result += M.write_math_style2(M.type_string(final_expression))
            result += M.write_new_line()

        elif ((self.kind_of_answer in ['sum', 'sum_not_reducible'])
              and self.expression.
              right_hand_side.expand_and_reduce_next_step() is None):
            # __
            result += M.write_math_style2(M.type_string(self.expression))
            result += M.write_new_line()
            result += M.write(_("This expression is not reducible."))
            result += M.write_new_line()

        else:
            result += M.write(self.expression.auto_expansion_and_reduction())

        return result