From: Cristian Armentano Date: Fri, 29 Jun 2007 14:12:07 +0000 (+0000) Subject: theorems about sigma_p proved using sigma_p_gen X-Git-Tag: make_still_working~6235 X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=commitdiff_plain;h=e0c0312bde81f2d47a7756e998ca8e9bd9f39832;p=helm.git theorems about sigma_p proved using sigma_p_gen --- diff --git a/helm/software/matita/library/Z/sigma_p.ma b/helm/software/matita/library/Z/sigma_p.ma index 24cb89395..5d85bc653 100644 --- a/helm/software/matita/library/Z/sigma_p.ma +++ b/helm/software/matita/library/Z/sigma_p.ma @@ -17,29 +17,36 @@ set "baseuri" "cic:/matita/Z/sigma_p.ma". include "Z/times.ma". include "nat/primes.ma". include "nat/ord.ma". +include "nat/generic_sigma_p.ma". -let rec sigma_p n p (g:nat \to Z) \def - match n with - [ O \Rightarrow OZ - | (S k) \Rightarrow - match p k with - [true \Rightarrow (g k)+(sigma_p k p g) - |false \Rightarrow sigma_p k p g] - ]. +(* sigma_p in Z is a specialization of sigma_p_gen *) +definition sigma_p: nat \to (nat \to bool) \to (nat \to Z) \to Z \def +\lambda n, p, g. (sigma_p_gen n p Z g OZ Zplus). +theorem symmetricZPlus: symmetric Z Zplus. +change with (\forall a,b:Z. (Zplus a b) = (Zplus b a)). +intros. +rewrite > sym_Zplus. +reflexivity. +qed. + theorem true_to_sigma_p_Sn: \forall n:nat. \forall p:nat \to bool. \forall g:nat \to Z. p n = true \to sigma_p (S n) p g = (g n)+(sigma_p n p g). -intros.simplify. -rewrite > H.reflexivity. +intros. +unfold sigma_p. +apply true_to_sigma_p_Sn_gen. +assumption. qed. theorem false_to_sigma_p_Sn: \forall n:nat. \forall p:nat \to bool. \forall g:nat \to Z. p n = false \to sigma_p (S n) p g = sigma_p n p g. -intros.simplify. -rewrite > H.reflexivity. +intros. +unfold sigma_p. +apply false_to_sigma_p_Sn_gen. +assumption. qed. theorem eq_sigma_p: \forall p1,p2:nat \to bool. @@ -47,32 +54,10 @@ theorem eq_sigma_p: \forall p1,p2:nat \to bool. (\forall x. x < n \to p1 x = p2 x) \to (\forall x. x < n \to g1 x = g2 x) \to sigma_p n p1 g1 = sigma_p n p2 g2. -intros 5.elim n - [reflexivity - |apply (bool_elim ? (p1 n1)) - [intro. - rewrite > (true_to_sigma_p_Sn ? ? ? H3). - rewrite > true_to_sigma_p_Sn - [apply eq_f2 - [apply H2.apply le_n. - |apply H - [intros.apply H1.apply le_S.assumption - |intros.apply H2.apply le_S.assumption - ] - ] - |rewrite < H3.apply sym_eq.apply H1.apply le_n - ] - |intro. - rewrite > (false_to_sigma_p_Sn ? ? ? H3). - rewrite > false_to_sigma_p_Sn - [apply H - [intros.apply H1.apply le_S.assumption - |intros.apply H2.apply le_S.assumption - ] - |rewrite < H3.apply sym_eq.apply H1.apply le_n - ] - ] - ] +intros. +unfold sigma_p. +apply eq_sigma_p_gen; + assumption. qed. theorem eq_sigma_p1: \forall p1,p2:nat \to bool. @@ -80,42 +65,17 @@ theorem eq_sigma_p1: \forall p1,p2:nat \to bool. (\forall x. x < n \to p1 x = p2 x) \to (\forall x. x < n \to p1 x = true \to g1 x = g2 x) \to sigma_p n p1 g1 = sigma_p n p2 g2. -intros 5. -elim n - [reflexivity - |apply (bool_elim ? (p1 n1)) - [intro. - rewrite > (true_to_sigma_p_Sn ? ? ? H3). - rewrite > true_to_sigma_p_Sn - [apply eq_f2 - [apply H2 - [apply le_n|assumption] - |apply H - [intros.apply H1.apply le_S.assumption - |intros.apply H2 - [apply le_S.assumption|assumption] - ] - ] - |rewrite < H3.apply sym_eq.apply H1.apply le_n - ] - |intro. - rewrite > (false_to_sigma_p_Sn ? ? ? H3). - rewrite > false_to_sigma_p_Sn - [apply H - [intros.apply H1.apply le_S.assumption - |intros.apply H2 - [apply le_S.assumption|assumption] - ] - |rewrite < H3.apply sym_eq.apply H1.apply le_n - ] - ] - ] +intros. +unfold sigma_p. +apply eq_sigma_p1_gen; + assumption. qed. theorem sigma_p_false: \forall g: nat \to Z.\forall n.sigma_p n (\lambda x.false) g = O. intros. -elim n[reflexivity|simplify.assumption] +unfold sigma_p. +apply sigma_p_false_gen. qed. theorem sigma_p_plus: \forall n,k:nat.\forall p:nat \to bool. @@ -123,41 +83,23 @@ theorem sigma_p_plus: \forall n,k:nat.\forall p:nat \to bool. sigma_p (k+n) p g = sigma_p k (\lambda x.p (x+n)) (\lambda x.g (x+n)) + sigma_p n p g. intros. -elim k - [reflexivity - |apply (bool_elim ? (p (n1+n))) - [intro. - simplify in \vdash (? ? (? % ? ?) ?). - rewrite > (true_to_sigma_p_Sn ? ? ? H1). - rewrite > (true_to_sigma_p_Sn n1 (\lambda x.p (x+n)) ? H1). - rewrite > assoc_Zplus. - rewrite < H.reflexivity - |intro. - simplify in \vdash (? ? (? % ? ?) ?). - rewrite > (false_to_sigma_p_Sn ? ? ? H1). - rewrite > (false_to_sigma_p_Sn n1 (\lambda x.p (x+n)) ? H1). - assumption. - ] - ] +unfold sigma_p. +apply (sigma_p_plusA_gen Z n k p g OZ Zplus) +[ apply symmetricZPlus. +| intros. + apply cic:/matita/Z/plus/Zplus_z_OZ.con +| apply associative_Zplus +] qed. theorem false_to_eq_sigma_p: \forall n,m:nat.n \le m \to \forall p:nat \to bool. \forall g: nat \to Z. (\forall i:nat. n \le i \to i < m \to p i = false) \to sigma_p m p g = sigma_p n p g. -intros 5. -elim H - [reflexivity - |simplify. - rewrite > H3 - [simplify. - apply H2. - intros. - apply H3[apply H4|apply le_S.assumption] - |assumption - |apply le_n - ] - ] +intros. +unfold sigma_p. +apply (false_to_eq_sigma_p_gen); + assumption. qed. theorem sigma_p2 : @@ -170,57 +112,17 @@ sigma_p (n*m) sigma_p n p1 (\lambda x.sigma_p m p2 (g x)). intros. -elim n - [simplify.reflexivity - |apply (bool_elim ? (p1 n1)) - [intro. - rewrite > (true_to_sigma_p_Sn ? ? ? H1). - simplify in \vdash (? ? (? % ? ?) ?); - rewrite > sigma_p_plus. - rewrite < H. - apply eq_f2 - [apply eq_sigma_p - [intros. - rewrite > sym_plus. - rewrite > (div_plus_times ? ? ? H2). - rewrite > (mod_plus_times ? ? ? H2). - rewrite > H1. - simplify.reflexivity - |intros. - rewrite > sym_plus. - rewrite > (div_plus_times ? ? ? H2). - rewrite > (mod_plus_times ? ? ? H2). - rewrite > H1. - simplify.reflexivity. - ] - |reflexivity - ] - |intro. - rewrite > (false_to_sigma_p_Sn ? ? ? H1). - simplify in \vdash (? ? (? % ? ?) ?); - rewrite > sigma_p_plus. - rewrite > H. - apply (trans_eq ? ? (O+(sigma_p n1 p1 (\lambda x:nat.sigma_p m p2 (g x))))) - [apply eq_f2 - [rewrite > (eq_sigma_p ? (\lambda x.false) ? (\lambda x:nat.g ((x+n1*m)/m) ((x+n1*m)\mod m))) - [apply sigma_p_false - |intros. - rewrite > sym_plus. - rewrite > (div_plus_times ? ? ? H2). - rewrite > (mod_plus_times ? ? ? H2). - rewrite > H1. - simplify.reflexivity - |intros.reflexivity. - ] - |reflexivity - ] - |reflexivity - ] - ] - ] +unfold sigma_p. +apply (sigma_p2_gen n m p1 p2 Z g OZ Zplus) +[ apply symmetricZPlus +| apply associative_Zplus +| intros. + apply Zplus_z_OZ +] qed. (* a stronger, dependent version, required e.g. for dirichlet product *) + theorem sigma_p2' : \forall n,m:nat. \forall p1:nat \to bool. @@ -232,129 +134,28 @@ sigma_p (n*m) sigma_p n p1 (\lambda x.sigma_p m (p2 x) (g x)). intros. -elim n - [simplify.reflexivity - |apply (bool_elim ? (p1 n1)) - [intro. - rewrite > (true_to_sigma_p_Sn ? ? ? H1). - simplify in \vdash (? ? (? % ? ?) ?); - rewrite > sigma_p_plus. - rewrite < H. - apply eq_f2 - [apply eq_sigma_p - [intros. - rewrite > sym_plus. - rewrite > (div_plus_times ? ? ? H2). - rewrite > (mod_plus_times ? ? ? H2). - rewrite > H1. - simplify.reflexivity - |intros. - rewrite > sym_plus. - rewrite > (div_plus_times ? ? ? H2). - rewrite > (mod_plus_times ? ? ? H2). - rewrite > H1. - simplify.reflexivity. - ] - |reflexivity - ] - |intro. - rewrite > (false_to_sigma_p_Sn ? ? ? H1). - simplify in \vdash (? ? (? % ? ?) ?); - rewrite > sigma_p_plus. - rewrite > H. - apply (trans_eq ? ? (O+(sigma_p n1 p1 (\lambda x:nat.sigma_p m (p2 x) (g x))))) - [apply eq_f2 - [rewrite > (eq_sigma_p ? (\lambda x.false) ? (\lambda x:nat.g ((x+n1*m)/m) ((x+n1*m)\mod m))) - [apply sigma_p_false - |intros. - rewrite > sym_plus. - rewrite > (div_plus_times ? ? ? H2). - rewrite > (mod_plus_times ? ? ? H2). - rewrite > H1. - simplify.reflexivity - |intros.reflexivity. - ] - |reflexivity - ] - |reflexivity - ] - ] - ] +unfold sigma_p. +apply (sigma_p2_gen' n m p1 p2 Z g OZ Zplus) +[ apply symmetricZPlus +| apply associative_Zplus +| intros. + apply Zplus_z_OZ +] qed. lemma sigma_p_gi: \forall g: nat \to Z. \forall n,i.\forall p:nat \to bool.i < n \to p i = true \to sigma_p n p g = g i + sigma_p n (\lambda x. andb (p x) (notb (eqb x i))) g. -intros 2. -elim n - [apply False_ind. - apply (not_le_Sn_O i). - assumption - |apply (bool_elim ? (p n1));intro - [elim (le_to_or_lt_eq i n1) - [rewrite > true_to_sigma_p_Sn - [rewrite > true_to_sigma_p_Sn - [rewrite < assoc_Zplus. - rewrite < sym_Zplus in \vdash (? ? ? (? % ?)). - rewrite > assoc_Zplus. - apply eq_f2 - [reflexivity - |apply H[assumption|assumption] - ] - |rewrite > H3.simplify. - change with (notb (eqb n1 i) = notb false). - apply eq_f. - apply not_eq_to_eqb_false. - unfold Not.intro. - apply (lt_to_not_eq ? ? H4). - apply sym_eq.assumption - ] - |assumption - ] - |rewrite > true_to_sigma_p_Sn - [rewrite > H4. - apply eq_f2 - [reflexivity - |rewrite > false_to_sigma_p_Sn - [apply eq_sigma_p - [intros. - elim (p x) - [simplify. - change with (notb false = notb (eqb x n1)). - apply eq_f. - apply sym_eq. - apply not_eq_to_eqb_false. - apply (lt_to_not_eq ? ? H5) - |reflexivity - ] - |intros.reflexivity - ] - |rewrite > H3. - rewrite > (eq_to_eqb_true ? ? (refl_eq ? n1)). - reflexivity - ] - ] - |assumption - ] - |apply le_S_S_to_le.assumption - ] - |rewrite > false_to_sigma_p_Sn - [elim (le_to_or_lt_eq i n1) - [rewrite > false_to_sigma_p_Sn - [apply H[assumption|assumption] - |rewrite > H3.reflexivity - ] - |apply False_ind. - apply not_eq_true_false. - rewrite < H2. - rewrite > H4. - assumption - |apply le_S_S_to_le.assumption - ] - |assumption - ] - ] - ] +intros. +unfold sigma_p. +apply (sigma_p_gi_gen) +[ apply symmetricZPlus +| apply associative_Zplus +| intros. + apply Zplus_z_OZ +| assumption +| assumption +] qed. theorem eq_sigma_p_gh: @@ -368,155 +169,58 @@ theorem eq_sigma_p_gh: (\forall j. j < n1 \to p2 j = true \to h (h1 j) = j) \to (\forall j. j < n1 \to p2 j = true \to h1 j < n) \to sigma_p n p1 (\lambda x.g(h x)) = sigma_p n1 (\lambda x.p2 x) g. -intros 4. -elim n - [generalize in match H5. - elim n1 - [reflexivity - |apply (bool_elim ? (p2 n2));intro - [apply False_ind. - apply (not_le_Sn_O (h1 n2)). - apply H7 - [apply le_n|assumption] - |rewrite > false_to_sigma_p_Sn - [apply H6. - intros. - apply H7[apply le_S.apply H9|assumption] - |assumption - ] - ] - ] - |apply (bool_elim ? (p1 n1));intro - [rewrite > true_to_sigma_p_Sn - [rewrite > (sigma_p_gi g n2 (h n1)) - [apply eq_f2 - [reflexivity - |apply H - [intros. - rewrite > H1 - [simplify. - change with ((\not eqb (h i) (h n1))= \not false). - apply eq_f. - apply not_eq_to_eqb_false. - unfold Not.intro. - apply (lt_to_not_eq ? ? H8). - rewrite < H2 - [rewrite < (H2 n1) - [apply eq_f.assumption|apply le_n|assumption] - |apply le_S.assumption - |assumption - ] - |apply le_S.assumption - |assumption - ] - |intros. - apply H2[apply le_S.assumption|assumption] - |intros. - apply H3[apply le_S.assumption|assumption] - |intros. - apply H4 - [assumption - |generalize in match H9. - elim (p2 j) - [reflexivity|assumption] - ] - |intros. - apply H5 - [assumption - |generalize in match H9. - elim (p2 j) - [reflexivity|assumption] - ] - |intros. - elim (le_to_or_lt_eq (h1 j) n1) - [assumption - |generalize in match H9. - elim (p2 j) - [simplify in H11. - absurd (j = (h n1)) - [rewrite < H10. - rewrite > H5 - [reflexivity|assumption|autobatch] - |apply eqb_false_to_not_eq. - generalize in match H11. - elim (eqb j (h n1)) - [apply sym_eq.assumption|reflexivity] - ] - |simplify in H11. - apply False_ind. - apply not_eq_true_false. - apply sym_eq.assumption - ] - |apply le_S_S_to_le. - apply H6 - [assumption - |generalize in match H9. - elim (p2 j) - [reflexivity|assumption] - ] - ] - ] - ] - |apply H3[apply le_n|assumption] - |apply H1[apply le_n|assumption] - ] - |assumption - ] - |rewrite > false_to_sigma_p_Sn - [apply H - [intros.apply H1[apply le_S.assumption|assumption] - |intros.apply H2[apply le_S.assumption|assumption] - |intros.apply H3[apply le_S.assumption|assumption] - |intros.apply H4[assumption|assumption] - |intros.apply H5[assumption|assumption] - |intros. - elim (le_to_or_lt_eq (h1 j) n1) - [assumption - |absurd (j = (h n1)) - [rewrite < H10. - rewrite > H5 - [reflexivity|assumption|assumption] - |unfold Not.intro. - apply not_eq_true_false. - rewrite < H7. - rewrite < H10. - rewrite > H4 - [reflexivity|assumption|assumption] - ] - |apply le_S_S_to_le. - apply H6[assumption|assumption] - ] - ] - |assumption - ] - ] - ] +intros. +unfold sigma_p. +apply (eq_sigma_p_gh_gen Z OZ Zplus ? ? ? g h h1 n n1 p1 p2) +[ apply symmetricZPlus +| apply associative_Zplus +| intros. + apply Zplus_z_OZ +| assumption +| assumption +| assumption +| assumption +| assumption +| assumption +] qed. + +theorem sigma_p_divides_b: +\forall n,m,p:nat.O < n \to prime p \to Not (divides p n) \to +\forall g: nat \to Z. +sigma_p (S (n*(exp p m))) (\lambda x.divides_b x (n*(exp p m))) g = +sigma_p (S n) (\lambda x.divides_b x n) + (\lambda x.sigma_p (S m) (\lambda y.true) (\lambda y.g (x*(exp p y)))). +intros. +unfold sigma_p. +apply (sigma_p_divides_gen Z OZ Zplus n m p ? ? ? g) +[ assumption +| assumption +| assumption +| apply symmetricZPlus +| apply associative_Zplus +| intros. + apply Zplus_z_OZ +] +qed. + + (* sigma_p and Ztimes *) lemma Ztimes_sigma_pl: \forall z:Z.\forall n:nat.\forall p. \forall f. z * (sigma_p n p f) = sigma_p n p (\lambda i.z*(f i)). intros. -elim n - [rewrite > Ztimes_z_OZ.reflexivity - |apply (bool_elim ? (p n1)); intro - [rewrite > true_to_sigma_p_Sn - [rewrite > true_to_sigma_p_Sn - [rewrite < H. - apply distr_Ztimes_Zplus - |assumption - ] - |assumption - ] - |rewrite > false_to_sigma_p_Sn - [rewrite > false_to_sigma_p_Sn - [assumption - |assumption - ] - |assumption - ] - ] - ] +apply (distributive_times_plus_sigma_p_generic Z Zplus OZ Ztimes n z p f) +[ apply symmetricZPlus +| apply associative_Zplus +| intros. + apply Zplus_z_OZ +| apply symmetric_Ztimes +| apply distributive_Ztimes_Zplus +| intros. + rewrite > (Ztimes_z_OZ a). + reflexivity +] qed. lemma Ztimes_sigma_pr: \forall z:Z.\forall n:nat.\forall p. \forall f. @@ -528,240 +232,4 @@ apply eq_sigma_p [intros.reflexivity |intros.apply sym_Ztimes ] -qed. - -theorem divides_exp_to_lt_ord:\forall n,m,j,p. O < n \to prime p \to -p \ndivides n \to j \divides n*(exp p m) \to ord j p < S m. -intros. -cut (m = ord (n*(exp p m)) p) - [apply le_S_S. - rewrite > Hcut. - apply divides_to_le_ord - [elim (le_to_or_lt_eq ? ? (le_O_n j)) - [assumption - |apply False_ind. - apply (lt_to_not_eq ? ? H). - elim H3. - rewrite < H4 in H5.simplify in H5. - elim (times_O_to_O ? ? H5) - [apply sym_eq.assumption - |apply False_ind. - apply (not_le_Sn_n O). - rewrite < H6 in \vdash (? ? %). - apply lt_O_exp. - elim H1.apply lt_to_le.assumption - ] - ] - |rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.apply (prime_to_lt_O ? H1)] - |assumption - |assumption - ] - |unfold ord. - rewrite > (p_ord_exp1 p ? m n) - [reflexivity - |apply (prime_to_lt_O ? H1) - |assumption - |apply sym_times - ] - ] -qed. - -theorem divides_exp_to_divides_ord_rem:\forall n,m,j,p. O < n \to prime p \to -p \ndivides n \to j \divides n*(exp p m) \to ord_rem j p \divides n. -intros. -cut (O < j) - [cut (n = ord_rem (n*(exp p m)) p) - [rewrite > Hcut1. - apply divides_to_divides_ord_rem - [assumption - |rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.apply (prime_to_lt_O ? H1)] - |assumption - |assumption - ] - |unfold ord_rem. - rewrite > (p_ord_exp1 p ? m n) - [reflexivity - |apply (prime_to_lt_O ? H1) - |assumption - |apply sym_times - ] - ] - |elim (le_to_or_lt_eq ? ? (le_O_n j)) - [assumption - |apply False_ind. - apply (lt_to_not_eq ? ? H). - elim H3. - rewrite < H4 in H5.simplify in H5. - elim (times_O_to_O ? ? H5) - [apply sym_eq.assumption - |apply False_ind. - apply (not_le_Sn_n O). - rewrite < H6 in \vdash (? ? %). - apply lt_O_exp. - elim H1.apply lt_to_le.assumption - ] - ] - ] -qed. - -theorem sigma_p_divides_b: -\forall n,m,p:nat.O < n \to prime p \to Not (divides p n) \to -\forall g: nat \to Z. -sigma_p (S (n*(exp p m))) (\lambda x.divides_b x (n*(exp p m))) g = -sigma_p (S n) (\lambda x.divides_b x n) - (\lambda x.sigma_p (S m) (\lambda y.true) (\lambda y.g (x*(exp p y)))). -intros. -cut (O < p) - [rewrite < sigma_p2. - apply (trans_eq ? ? - (sigma_p (S n*S m) (\lambda x:nat.divides_b (x/S m) n) - (\lambda x:nat.g (x/S m*(p)\sup(x\mod S m))))) - [apply sym_eq. - apply (eq_sigma_p_gh g ? (p_ord_inv p (S m))) - [intros. - lapply (divides_b_true_to_lt_O ? ? H H4). - apply divides_to_divides_b_true - [rewrite > (times_n_O O). - apply lt_times - [assumption - |apply lt_O_exp.assumption - ] - |apply divides_times - [apply divides_b_true_to_divides.assumption - |apply (witness ? ? (p \sup (m-i \mod (S m)))). - rewrite < exp_plus_times. - apply eq_f. - rewrite > sym_plus. - apply plus_minus_m_m. - autobatch - ] - ] - |intros. - lapply (divides_b_true_to_lt_O ? ? H H4). - unfold p_ord_inv. - rewrite > (p_ord_exp1 p ? (i \mod (S m)) (i/S m)) - [change with ((i/S m)*S m+i \mod S m=i). - apply sym_eq. - apply div_mod. - apply lt_O_S - |assumption - |unfold Not.intro. - apply H2. - apply (trans_divides ? (i/ S m)) - [assumption| - apply divides_b_true_to_divides;assumption] - |apply sym_times. - ] - |intros. - apply le_S_S. - apply le_times - [apply le_S_S_to_le. - change with ((i/S m) < S n). - apply (lt_times_to_lt_l m). - apply (le_to_lt_to_lt ? i) - [autobatch|assumption] - |apply le_exp - [assumption - |apply le_S_S_to_le. - apply lt_mod_m_m. - apply lt_O_S - ] - ] - |intros. - cut (ord j p < S m) - [rewrite > div_p_ord_inv - [apply divides_to_divides_b_true - [apply lt_O_ord_rem - [elim H1.assumption - |apply (divides_b_true_to_lt_O ? ? ? H4). - rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - ] - |apply (divides_exp_to_divides_ord_rem ? m ? ? H H1 H2). - apply divides_b_true_to_divides. - assumption - ] - |assumption - ] - |apply (divides_exp_to_lt_ord ? ? ? ? H H1 H2). - apply (divides_b_true_to_divides ? ? H4). - apply (divides_b_true_to_lt_O ? ? H4) - ] - |intros. - cut (ord j p < S m) - [rewrite > div_p_ord_inv - [rewrite > mod_p_ord_inv - [rewrite > sym_times. - apply sym_eq. - apply exp_ord - [elim H1.assumption - |apply (divides_b_true_to_lt_O ? ? ? H4). - rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - ] - |apply (divides_exp_to_lt_ord ? ? ? ? H H1 H2). - apply (divides_b_true_to_divides ? ? H4). - apply (divides_b_true_to_lt_O ? ? H4) - ] - |assumption - ] - |apply (divides_exp_to_lt_ord ? ? ? ? H H1 H2). - apply (divides_b_true_to_divides ? ? H4). - apply (divides_b_true_to_lt_O ? ? H4). - ] - |intros. - rewrite > eq_p_ord_inv. - rewrite > sym_plus. - apply (lt_to_le_to_lt ? (S m +ord_rem j p*S m)) - [apply lt_plus_l. - apply le_S_S. - cut (m = ord (n*(p \sup m)) p) - [rewrite > Hcut1. - apply divides_to_le_ord - [apply (divides_b_true_to_lt_O ? ? ? H4). - rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |assumption - |apply divides_b_true_to_divides. - assumption - ] - |unfold ord. - rewrite > sym_times. - rewrite > (p_ord_exp1 p ? m n) - [reflexivity - |assumption - |assumption - |reflexivity - ] - ] - |change with (S (ord_rem j p)*S m \le S n*S m). - apply le_times_l. - apply le_S_S. - apply divides_to_le - [assumption - |apply (divides_exp_to_divides_ord_rem ? m ? ? H H1 H2). - apply divides_b_true_to_divides. - assumption - ] - ] - ] - |apply eq_sigma_p - [intros. - elim (divides_b (x/S m) n);reflexivity - |intros.reflexivity - ] - ] - |elim H1.apply lt_to_le.assumption - ] -qed. - +qed. \ No newline at end of file diff --git a/helm/software/matita/library/nat/iteration2.ma b/helm/software/matita/library/nat/iteration2.ma index 14e14b263..e1cd09a20 100644 --- a/helm/software/matita/library/nat/iteration2.ma +++ b/helm/software/matita/library/nat/iteration2.ma @@ -16,29 +16,41 @@ set "baseuri" "cic:/matita/nat/iteration2.ma". include "nat/primes.ma". include "nat/ord.ma". +include "nat/generic_sigma_p.ma". -let rec sigma_p n p (g:nat \to nat) \def - match n with - [ O \Rightarrow O - | (S k) \Rightarrow - match p k with - [true \Rightarrow (g k)+(sigma_p k p g) - |false \Rightarrow sigma_p k p g] - ]. + +(* sigma_p on nautral numbers is a specialization of sigma_p_gen *) +definition sigma_p: nat \to (nat \to bool) \to (nat \to nat) \to nat \def +\lambda n, p, g. (sigma_p_gen n p nat g O plus). + +theorem symmetricIntPlus: symmetric nat plus. +change with (\forall a,b:nat. (plus a b) = (plus b a)). +intros. +rewrite > sym_plus. +reflexivity. +qed. +(*the following theorems on sigma_p in N are obtained by the more general ones + * in sigma_p_gen.ma + *) theorem true_to_sigma_p_Sn: \forall n:nat. \forall p:nat \to bool. \forall g:nat \to nat. p n = true \to sigma_p (S n) p g = (g n)+(sigma_p n p g). -intros.simplify. -rewrite > H.reflexivity. +intros. +unfold sigma_p. +apply true_to_sigma_p_Sn_gen. +assumption. qed. theorem false_to_sigma_p_Sn: \forall n:nat. \forall p:nat \to bool. \forall g:nat \to nat. p n = false \to sigma_p (S n) p g = sigma_p n p g. -intros.simplify. -rewrite > H.reflexivity. +intros. +unfold sigma_p. +apply false_to_sigma_p_Sn_gen. +assumption. + qed. theorem eq_sigma_p: \forall p1,p2:nat \to bool. @@ -46,38 +58,28 @@ theorem eq_sigma_p: \forall p1,p2:nat \to bool. (\forall x. x < n \to p1 x = p2 x) \to (\forall x. x < n \to g1 x = g2 x) \to sigma_p n p1 g1 = sigma_p n p2 g2. -intros 5.elim n - [reflexivity - |apply (bool_elim ? (p1 n1)) - [intro. - rewrite > (true_to_sigma_p_Sn ? ? ? H3). - rewrite > true_to_sigma_p_Sn - [apply eq_f2 - [apply H2.apply le_n. - |apply H - [intros.apply H1.apply le_S.assumption - |intros.apply H2.apply le_S.assumption - ] - ] - |rewrite < H3.apply sym_eq.apply H1.apply le_n - ] - |intro. - rewrite > (false_to_sigma_p_Sn ? ? ? H3). - rewrite > false_to_sigma_p_Sn - [apply H - [intros.apply H1.apply le_S.assumption - |intros.apply H2.apply le_S.assumption - ] - |rewrite < H3.apply sym_eq.apply H1.apply le_n - ] - ] - ] +intros. +unfold sigma_p. +apply eq_sigma_p_gen; + assumption. +qed. + +theorem eq_sigma_p1: \forall p1,p2:nat \to bool. +\forall g1,g2: nat \to nat.\forall n. +(\forall x. x < n \to p1 x = p2 x) \to +(\forall x. x < n \to p1 x = true \to g1 x = g2 x) \to +sigma_p n p1 g1 = sigma_p n p2 g2. +intros. +unfold sigma_p. +apply eq_sigma_p1_gen; + assumption. qed. theorem sigma_p_false: \forall g: nat \to nat.\forall n.sigma_p n (\lambda x.false) g = O. intros. -elim n[reflexivity|simplify.assumption] +unfold sigma_p. +apply sigma_p_false_gen. qed. theorem sigma_p_plus: \forall n,k:nat.\forall p:nat \to bool. @@ -85,41 +87,24 @@ theorem sigma_p_plus: \forall n,k:nat.\forall p:nat \to bool. sigma_p (k+n) p g = sigma_p k (\lambda x.p (x+n)) (\lambda x.g (x+n)) + sigma_p n p g. intros. -elim k - [reflexivity - |apply (bool_elim ? (p (n1+n))) - [intro. - simplify in \vdash (? ? (? % ? ?) ?). - rewrite > (true_to_sigma_p_Sn ? ? ? H1). - rewrite > (true_to_sigma_p_Sn n1 (\lambda x.p (x+n)) ? H1). - rewrite > assoc_plus. - rewrite < H.reflexivity - |intro. - simplify in \vdash (? ? (? % ? ?) ?). - rewrite > (false_to_sigma_p_Sn ? ? ? H1). - rewrite > (false_to_sigma_p_Sn n1 (\lambda x.p (x+n)) ? H1). - assumption. - ] - ] +unfold sigma_p. +apply (sigma_p_plusA_gen nat n k p g O plus) +[ apply symmetricIntPlus. +| intros. + apply sym_eq. + apply plus_n_O +| apply associative_plus +] qed. theorem false_to_eq_sigma_p: \forall n,m:nat.n \le m \to \forall p:nat \to bool. \forall g: nat \to nat. (\forall i:nat. n \le i \to i < m \to p i = false) \to sigma_p m p g = sigma_p n p g. -intros 5. -elim H - [reflexivity - |simplify. - rewrite > H3 - [simplify. - apply H2. - intros. - apply H3[apply H4|apply le_S.assumption] - |assumption - |apply le_n - ] - ] +intros. +unfold sigma_p. +apply (false_to_eq_sigma_p_gen); + assumption. qed. theorem sigma_p2 : @@ -132,129 +117,51 @@ sigma_p (n*m) sigma_p n p1 (\lambda x.sigma_p m p2 (g x)). intros. -elim n - [simplify.reflexivity - |apply (bool_elim ? (p1 n1)) - [intro. - rewrite > (true_to_sigma_p_Sn ? ? ? H1). - simplify in \vdash (? ? (? % ? ?) ?); - rewrite > sigma_p_plus. - rewrite < H. - apply eq_f2 - [apply eq_sigma_p - [intros. - rewrite > sym_plus. - rewrite > (div_plus_times ? ? ? H2). - rewrite > (mod_plus_times ? ? ? H2). - rewrite > H1. - simplify.reflexivity - |intros. - rewrite > sym_plus. - rewrite > (div_plus_times ? ? ? H2). - rewrite > (mod_plus_times ? ? ? H2). - rewrite > H1. - simplify.reflexivity. - ] - |reflexivity - ] - |intro. - rewrite > (false_to_sigma_p_Sn ? ? ? H1). - simplify in \vdash (? ? (? % ? ?) ?); - rewrite > sigma_p_plus. - rewrite > H. - apply (trans_eq ? ? (O+(sigma_p n1 p1 (\lambda x:nat.sigma_p m p2 (g x))))) - [apply eq_f2 - [rewrite > (eq_sigma_p ? (\lambda x.false) ? (\lambda x:nat.g ((x+n1*m)/m) ((x+n1*m)\mod m))) - [apply sigma_p_false - |intros. - rewrite > sym_plus. - rewrite > (div_plus_times ? ? ? H2). - rewrite > (mod_plus_times ? ? ? H2). - rewrite > H1. - simplify.reflexivity - |intros.reflexivity. - ] - |reflexivity - ] - |reflexivity - ] - ] - ] +unfold sigma_p. +apply (sigma_p2_gen n m p1 p2 nat g O plus) +[ apply symmetricIntPlus +| apply associative_plus +| intros. + apply sym_eq. + apply plus_n_O +] +qed. + +theorem sigma_p2' : +\forall n,m:nat. +\forall p1:nat \to bool. +\forall p2:nat \to nat \to bool. +\forall g: nat \to nat \to nat. +sigma_p (n*m) + (\lambda x.andb (p1 (div x m)) (p2 (div x m) (mod x m))) + (\lambda x.g (div x m) (mod x m)) = +sigma_p n p1 + (\lambda x.sigma_p m (p2 x) (g x)). +intros. +unfold sigma_p. +apply (sigma_p2_gen' n m p1 p2 nat g O plus) +[ apply symmetricIntPlus +| apply associative_plus +| intros. + apply sym_eq. + apply plus_n_O +] qed. lemma sigma_p_gi: \forall g: nat \to nat. \forall n,i.\forall p:nat \to bool.i < n \to p i = true \to sigma_p n p g = g i + sigma_p n (\lambda x. andb (p x) (notb (eqb x i))) g. -intros 2. -elim n - [apply False_ind. - apply (not_le_Sn_O i). - assumption - |apply (bool_elim ? (p n1));intro - [elim (le_to_or_lt_eq i n1) - [rewrite > true_to_sigma_p_Sn - [rewrite > true_to_sigma_p_Sn - [rewrite < assoc_plus. - rewrite < sym_plus in \vdash (? ? ? (? % ?)). - rewrite > assoc_plus. - apply eq_f2 - [reflexivity - |apply H[assumption|assumption] - ] - |rewrite > H3.simplify. - change with (notb (eqb n1 i) = notb false). - apply eq_f. - apply not_eq_to_eqb_false. - unfold Not.intro. - apply (lt_to_not_eq ? ? H4). - apply sym_eq.assumption - ] - |assumption - ] - |rewrite > true_to_sigma_p_Sn - [rewrite > H4. - apply eq_f2 - [reflexivity - |rewrite > false_to_sigma_p_Sn - [apply eq_sigma_p - [intros. - elim (p x) - [simplify. - change with (notb false = notb (eqb x n1)). - apply eq_f. - apply sym_eq. - apply not_eq_to_eqb_false. - apply (lt_to_not_eq ? ? H5) - |reflexivity - ] - |intros.reflexivity - ] - |rewrite > H3. - rewrite > (eq_to_eqb_true ? ? (refl_eq ? n1)). - reflexivity - ] - ] - |assumption - ] - |apply le_S_S_to_le.assumption - ] - |rewrite > false_to_sigma_p_Sn - [elim (le_to_or_lt_eq i n1) - [rewrite > false_to_sigma_p_Sn - [apply H[assumption|assumption] - |rewrite > H3.reflexivity - ] - |apply False_ind. - apply not_eq_true_false. - rewrite < H2. - rewrite > H4. - assumption - |apply le_S_S_to_le.assumption - ] - |assumption - ] - ] - ] +intros. +unfold sigma_p. +apply (sigma_p_gi_gen) +[ apply symmetricIntPlus +| apply associative_plus +| intros. + apply sym_eq. + apply plus_n_O +| assumption +| assumption +] qed. theorem eq_sigma_p_gh: @@ -267,157 +174,23 @@ theorem eq_sigma_p_gh: (\forall j. j < n1 \to p2 j = true \to h (h1 j) = j) \to (\forall j. j < n1 \to p2 j = true \to h1 j < n) \to sigma_p n p1 (\lambda x.g(h x)) = sigma_p n1 (\lambda x.p2 x) g. -intros 4. -elim n - [generalize in match H5. - elim n1 - [reflexivity - |apply (bool_elim ? (p2 n2));intro - [apply False_ind. - apply (not_le_Sn_O (h1 n2)). - apply H7 - [apply le_n|assumption] - |rewrite > false_to_sigma_p_Sn - [apply H6. - intros. - apply H7[apply le_S.apply H9|assumption] - |assumption - ] - ] - ] - |apply (bool_elim ? (p1 n1));intro - [rewrite > true_to_sigma_p_Sn - [rewrite > (sigma_p_gi g n2 (h n1)) - [apply eq_f2 - [reflexivity - |apply H - [intros. - rewrite > H1 - [simplify. - change with ((\not eqb (h i) (h n1))= \not false). - apply eq_f. - apply not_eq_to_eqb_false. - unfold Not.intro. - apply (lt_to_not_eq ? ? H8). - rewrite < H2 - [rewrite < (H2 n1) - [apply eq_f.assumption|apply le_n|assumption] - |apply le_S.assumption - |assumption - ] - |apply le_S.assumption - |assumption - ] - |intros. - apply H2[apply le_S.assumption|assumption] - |intros. - apply H3[apply le_S.assumption|assumption] - |intros. - apply H4 - [assumption - |generalize in match H9. - elim (p2 j) - [reflexivity|assumption] - ] - |intros. - apply H5 - [assumption - |generalize in match H9. - elim (p2 j) - [reflexivity|assumption] - ] - |intros. - elim (le_to_or_lt_eq (h1 j) n1) - [assumption - |generalize in match H9. - elim (p2 j) - [simplify in H11. - absurd (j = (h n1)) - [rewrite < H10. - rewrite > H5 - [reflexivity|assumption|autobatch] - |apply eqb_false_to_not_eq. - generalize in match H11. - elim (eqb j (h n1)) - [apply sym_eq.assumption|reflexivity] - ] - |simplify in H11. - apply False_ind. - apply not_eq_true_false. - apply sym_eq.assumption - ] - |apply le_S_S_to_le. - apply H6 - [assumption - |generalize in match H9. - elim (p2 j) - [reflexivity|assumption] - ] - ] - ] - ] - |apply H3[apply le_n|assumption] - |apply H1[apply le_n|assumption] - ] - |assumption - ] - |rewrite > false_to_sigma_p_Sn - [apply H - [intros.apply H1[apply le_S.assumption|assumption] - |intros.apply H2[apply le_S.assumption|assumption] - |intros.apply H3[apply le_S.assumption|assumption] - |intros.apply H4[assumption|assumption] - |intros.apply H5[assumption|assumption] - |intros. - elim (le_to_or_lt_eq (h1 j) n1) - [assumption - |absurd (j = (h n1)) - [rewrite < H10. - rewrite > H5 - [reflexivity|assumption|assumption] - |unfold Not.intro. - apply not_eq_true_false. - rewrite < H7. - rewrite < H10. - rewrite > H4 - [reflexivity|assumption|assumption] - ] - |apply le_S_S_to_le. - apply H6[assumption|assumption] - ] - ] - |assumption - ] - ] - ] -qed. - -definition p_ord_times \def -\lambda p,m,x. - match p_ord x p with - [pair q r \Rightarrow r*m+q]. - -theorem eq_p_ord_times: \forall p,m,x. -p_ord_times p m x = (ord_rem x p)*m+(ord x p). -intros.unfold p_ord_times. unfold ord_rem. -unfold ord. -elim (p_ord x p). -reflexivity. +intros. +unfold sigma_p. +apply (eq_sigma_p_gh_gen nat O plus ? ? ? g h h1 n n1 p1 p2) +[ apply symmetricIntPlus +| apply associative_plus +| intros. + apply sym_eq. + apply plus_n_O +| assumption +| assumption +| assumption +| assumption +| assumption +| assumption +] qed. -theorem div_p_ord_times: -\forall p,m,x. ord x p < m \to p_ord_times p m x / m = ord_rem x p. -intros.rewrite > eq_p_ord_times. -apply div_plus_times. -assumption. -qed. - -theorem mod_p_ord_times: -\forall p,m,x. ord x p < m \to p_ord_times p m x \mod m = ord x p. -intros.rewrite > eq_p_ord_times. -apply mod_plus_times. -assumption. -qed. theorem sigma_p_divides: \forall n,m,p:nat.O < n \to prime p \to Not (divides p n) \to @@ -426,258 +199,33 @@ sigma_p (S (n*(exp p m))) (\lambda x.divides_b x (n*(exp p m))) g = sigma_p (S n) (\lambda x.divides_b x n) (\lambda x.sigma_p (S m) (\lambda y.true) (\lambda y.g (x*(exp p y)))). intros. -cut (O < p) - [rewrite < sigma_p2. - apply (trans_eq ? ? - (sigma_p (S n*S m) (\lambda x:nat.divides_b (x/S m) n) - (\lambda x:nat.g (x/S m*(p)\sup(x\mod S m))))) - [apply sym_eq. - apply (eq_sigma_p_gh g ? (p_ord_times p (S m))) - [intros. - lapply (divides_b_true_to_lt_O ? ? H H4). - apply divides_to_divides_b_true - [rewrite > (times_n_O O). - apply lt_times - [assumption - |apply lt_O_exp.assumption - ] - |apply divides_times - [apply divides_b_true_to_divides.assumption - |apply (witness ? ? (p \sup (m-i \mod (S m)))). - rewrite < exp_plus_times. - apply eq_f. - rewrite > sym_plus. - apply plus_minus_m_m. - autobatch - ] - ] - |intros. - lapply (divides_b_true_to_lt_O ? ? H H4). - unfold p_ord_times. - rewrite > (p_ord_exp1 p ? (i \mod (S m)) (i/S m)) - [change with ((i/S m)*S m+i \mod S m=i). - apply sym_eq. - apply div_mod. - apply lt_O_S - |assumption - |unfold Not.intro. - apply H2. - apply (trans_divides ? (i/ S m)) - [assumption| - apply divides_b_true_to_divides;assumption] - |apply sym_times. - ] - |intros. - apply le_S_S. - apply le_times - [apply le_S_S_to_le. - change with ((i/S m) < S n). - apply (lt_times_to_lt_l m). - apply (le_to_lt_to_lt ? i) - [autobatch|assumption] - |apply le_exp - [assumption - |apply le_S_S_to_le. - apply lt_mod_m_m. - apply lt_O_S - ] - ] - |intros. - cut (ord j p < S m) - [rewrite > div_p_ord_times - [apply divides_to_divides_b_true - [apply lt_O_ord_rem - [elim H1.assumption - |apply (divides_b_true_to_lt_O ? ? ? H4). - rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - ] - |cut (n = ord_rem (n*(exp p m)) p) - [rewrite > Hcut2. - apply divides_to_divides_ord_rem - [apply (divides_b_true_to_lt_O ? ? ? H4). - rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |assumption - |apply divides_b_true_to_divides. - assumption - ] - |unfold ord_rem. - rewrite > (p_ord_exp1 p ? m n) - [reflexivity - |assumption - |assumption - |apply sym_times - ] - ] - ] - |assumption - ] - |cut (m = ord (n*(exp p m)) p) - [apply le_S_S. - rewrite > Hcut1. - apply divides_to_le_ord - [apply (divides_b_true_to_lt_O ? ? ? H4). - rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |assumption - |apply divides_b_true_to_divides. - assumption - ] - |unfold ord. - rewrite > (p_ord_exp1 p ? m n) - [reflexivity - |assumption - |assumption - |apply sym_times - ] - ] - ] - |intros. - cut (ord j p < S m) - [rewrite > div_p_ord_times - [rewrite > mod_p_ord_times - [rewrite > sym_times. - apply sym_eq. - apply exp_ord - [elim H1.assumption - |apply (divides_b_true_to_lt_O ? ? ? H4). - rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - ] - |cut (m = ord (n*(exp p m)) p) - [apply le_S_S. - rewrite > Hcut2. - apply divides_to_le_ord - [apply (divides_b_true_to_lt_O ? ? ? H4). - rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |assumption - |apply divides_b_true_to_divides. - assumption - ] - |unfold ord. - rewrite > (p_ord_exp1 p ? m n) - [reflexivity - |assumption - |assumption - |apply sym_times - ] - ] - ] - |assumption - ] - |cut (m = ord (n*(exp p m)) p) - [apply le_S_S. - rewrite > Hcut1. - apply divides_to_le_ord - [apply (divides_b_true_to_lt_O ? ? ? H4). - rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |assumption - |apply divides_b_true_to_divides. - assumption - ] - |unfold ord. - rewrite > (p_ord_exp1 p ? m n) - [reflexivity - |assumption - |assumption - |apply sym_times - ] - ] - ] - |intros. - rewrite > eq_p_ord_times. - rewrite > sym_plus. - apply (lt_to_le_to_lt ? (S m +ord_rem j p*S m)) - [apply lt_plus_l. - apply le_S_S. - cut (m = ord (n*(p \sup m)) p) - [rewrite > Hcut1. - apply divides_to_le_ord - [apply (divides_b_true_to_lt_O ? ? ? H4). - rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |assumption - |apply divides_b_true_to_divides. - assumption - ] - |unfold ord. - rewrite > sym_times. - rewrite > (p_ord_exp1 p ? m n) - [reflexivity - |assumption - |assumption - |reflexivity - ] - ] - |change with (S (ord_rem j p)*S m \le S n*S m). - apply le_times_l. - apply le_S_S. - cut (n = ord_rem (n*(p \sup m)) p) - [rewrite > Hcut1. - apply divides_to_le - [apply lt_O_ord_rem - [elim H1.assumption - |rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - ] - |apply divides_to_divides_ord_rem - [apply (divides_b_true_to_lt_O ? ? ? H4). - rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |rewrite > (times_n_O O). - apply lt_times - [assumption|apply lt_O_exp.assumption] - |assumption - |apply divides_b_true_to_divides. - assumption - ] - ] - |unfold ord_rem. - rewrite > sym_times. - rewrite > (p_ord_exp1 p ? m n) - [reflexivity - |assumption - |assumption - |reflexivity - ] - ] - ] - ] - |apply eq_sigma_p - [intros. - elim (divides_b (x/S m) n);reflexivity - |intros.reflexivity - ] - ] -|elim H1.apply lt_to_le.assumption +unfold sigma_p. +apply (sigma_p_divides_gen nat O plus n m p ? ? ? g) +[ assumption +| assumption +| assumption +| apply symmetricIntPlus +| apply associative_plus +| intros. + apply sym_eq. + apply plus_n_O +] +qed. + +theorem distributive_times_plus_sigma_p: \forall n,k:nat. \forall p:nat \to bool. \forall g:nat \to nat. +k*(sigma_p n p g) = sigma_p n p (\lambda i:nat.k * (g i)). +intros. +apply (distributive_times_plus_sigma_p_generic nat plus O times n k p g) +[ apply symmetricIntPlus +| apply associative_plus +| intros. + apply sym_eq. + apply plus_n_O +| apply symmetric_times +| apply distributive_times_plus +| intros. + rewrite < (times_n_O a). + reflexivity ] qed. -