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norm_num.lean
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norm_num.lean
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/-
Copyright (c) 2017 Simon Hudon All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Simon Hudon, Mario Carneiro
-/
import data.rat.cast
import data.rat.meta_defs
import data.int.lemmas
/-!
# `norm_num`
Evaluating arithmetic expressions including `*`, `+`, `-`, `^`, `≤`.
-/
universes u v w
namespace tactic
namespace instance_cache
/-- Faster version of `mk_app ``bit0 [e]`. -/
meta def mk_bit0 (c : instance_cache) (e : expr) : tactic (instance_cache × expr) :=
do (c, ai) ← c.get ``has_add,
return (c, (expr.const ``bit0 [c.univ]).mk_app [c.α, ai, e])
/-- Faster version of `mk_app ``bit1 [e]`. -/
meta def mk_bit1 (c : instance_cache) (e : expr) : tactic (instance_cache × expr) :=
do (c, ai) ← c.get ``has_add,
(c, oi) ← c.get ``has_one,
return (c, (expr.const ``bit1 [c.univ]).mk_app [c.α, oi, ai, e])
end instance_cache
end tactic
open tactic
/-!
Each lemma in this file is written the way it is to exactly match (with no defeq reduction allowed)
the conclusion of some lemma generated by the proof procedure that uses it. That proof procedure
should describe the shape of the generated lemma in its docstring.
-/
namespace norm_num
variable {α : Type u}
lemma subst_into_add {α} [has_add α] (l r tl tr t)
(prl : (l : α) = tl) (prr : r = tr) (prt : tl + tr = t) : l + r = t :=
by rw [prl, prr, prt]
lemma subst_into_mul {α} [has_mul α] (l r tl tr t)
(prl : (l : α) = tl) (prr : r = tr) (prt : tl * tr = t) : l * r = t :=
by rw [prl, prr, prt]
lemma subst_into_neg {α} [has_neg α] (a ta t : α) (pra : a = ta) (prt : -ta = t) : -a = t :=
by simp [pra, prt]
/-- The result type of `match_numeral`, either `0`, `1`, or a top level
decomposition of `bit0 e` or `bit1 e`. The `other` case means it is not a numeral. -/
meta inductive match_numeral_result
| zero | one | bit0 (e : expr) | bit1 (e : expr) | other
/-- Unfold the top level constructor of the numeral expression. -/
meta def match_numeral : expr → match_numeral_result
| `(bit0 %%e) := match_numeral_result.bit0 e
| `(bit1 %%e) := match_numeral_result.bit1 e
| `(@has_zero.zero _ _) := match_numeral_result.zero
| `(@has_one.one _ _) := match_numeral_result.one
| _ := match_numeral_result.other
theorem zero_succ {α} [semiring α] : (0 + 1 : α) = 1 := zero_add _
theorem one_succ {α} [semiring α] : (1 + 1 : α) = 2 := rfl
theorem bit0_succ {α} [semiring α] (a : α) : bit0 a + 1 = bit1 a := rfl
theorem bit1_succ {α} [semiring α] (a b : α) (h : a + 1 = b) : bit1 a + 1 = bit0 b :=
h ▸ by simp [bit1, bit0, add_left_comm, add_assoc]
section
open match_numeral_result
/-- Given `a`, `b` natural numerals, proves `⊢ a + 1 = b`, assuming that this is provable.
(It may prove garbage instead of failing if `a + 1 = b` is false.) -/
meta def prove_succ : instance_cache → expr → expr → tactic (instance_cache × expr)
| c e r := match match_numeral e with
| zero := c.mk_app ``zero_succ []
| one := c.mk_app ``one_succ []
| bit0 e := c.mk_app ``bit0_succ [e]
| bit1 e := do
let r := r.app_arg,
(c, p) ← prove_succ c e r,
c.mk_app ``bit1_succ [e, r, p]
| _ := failed
end
end
/-- Given `a` natural numeral, returns `(b, ⊢ a + 1 = b)`. -/
meta def prove_succ' (c : instance_cache) (a : expr) : tactic (instance_cache × expr × expr) :=
do na ← a.to_nat,
(c, b) ← c.of_nat (na + 1),
(c, p) ← prove_succ c a b,
return (c, b, p)
theorem zero_adc {α} [semiring α] (a b : α) (h : a + 1 = b) : 0 + a + 1 = b := by rwa zero_add
theorem adc_zero {α} [semiring α] (a b : α) (h : a + 1 = b) : a + 0 + 1 = b := by rwa add_zero
theorem one_add {α} [semiring α] (a b : α) (h : a + 1 = b) : 1 + a = b := by rwa add_comm
theorem add_bit0_bit0 {α} [semiring α] (a b c : α) (h : a + b = c) : bit0 a + bit0 b = bit0 c :=
h ▸ by simp [bit0, add_left_comm, add_assoc]
theorem add_bit0_bit1 {α} [semiring α] (a b c : α) (h : a + b = c) : bit0 a + bit1 b = bit1 c :=
h ▸ by simp [bit0, bit1, add_left_comm, add_assoc]
theorem add_bit1_bit0 {α} [semiring α] (a b c : α) (h : a + b = c) : bit1 a + bit0 b = bit1 c :=
h ▸ by simp [bit0, bit1, add_left_comm, add_comm, add_assoc]
theorem add_bit1_bit1 {α} [semiring α] (a b c : α) (h : a + b + 1 = c) : bit1 a + bit1 b = bit0 c :=
h ▸ by simp [bit0, bit1, add_left_comm, add_comm, add_assoc]
theorem adc_one_one {α} [semiring α] : (1 + 1 + 1 : α) = 3 := rfl
theorem adc_bit0_one {α} [semiring α] (a b : α) (h : a + 1 = b) : bit0 a + 1 + 1 = bit0 b :=
h ▸ by simp [bit0, add_left_comm, add_assoc]
theorem adc_one_bit0 {α} [semiring α] (a b : α) (h : a + 1 = b) : 1 + bit0 a + 1 = bit0 b :=
h ▸ by simp [bit0, add_left_comm, add_assoc]
theorem adc_bit1_one {α} [semiring α] (a b : α) (h : a + 1 = b) : bit1 a + 1 + 1 = bit1 b :=
h ▸ by simp [bit1, bit0, add_left_comm, add_assoc]
theorem adc_one_bit1 {α} [semiring α] (a b : α) (h : a + 1 = b) : 1 + bit1 a + 1 = bit1 b :=
h ▸ by simp [bit1, bit0, add_left_comm, add_assoc]
theorem adc_bit0_bit0 {α} [semiring α] (a b c : α) (h : a + b = c) : bit0 a + bit0 b + 1 = bit1 c :=
h ▸ by simp [bit1, bit0, add_left_comm, add_assoc]
theorem adc_bit1_bit0 {α} [semiring α] (a b c : α) (h : a + b + 1 = c) :
bit1 a + bit0 b + 1 = bit0 c :=
h ▸ by simp [bit1, bit0, add_left_comm, add_assoc]
theorem adc_bit0_bit1 {α} [semiring α] (a b c : α) (h : a + b + 1 = c) :
bit0 a + bit1 b + 1 = bit0 c :=
h ▸ by simp [bit1, bit0, add_left_comm, add_assoc]
theorem adc_bit1_bit1 {α} [semiring α] (a b c : α) (h : a + b + 1 = c) :
bit1 a + bit1 b + 1 = bit1 c :=
h ▸ by simp [bit1, bit0, add_left_comm, add_assoc]
section
open match_numeral_result
meta mutual def prove_add_nat, prove_adc_nat
with prove_add_nat : instance_cache → expr → expr → expr → tactic (instance_cache × expr)
| c a b r := do
match match_numeral a, match_numeral b with
| zero, _ := c.mk_app ``zero_add [b]
| _, zero := c.mk_app ``add_zero [a]
| _, one := prove_succ c a r
| one, _ := do (c, p) ← prove_succ c b r, c.mk_app ``one_add [b, r, p]
| bit0 a, bit0 b :=
do let r := r.app_arg, (c, p) ← prove_add_nat c a b r, c.mk_app ``add_bit0_bit0 [a, b, r, p]
| bit0 a, bit1 b :=
do let r := r.app_arg, (c, p) ← prove_add_nat c a b r, c.mk_app ``add_bit0_bit1 [a, b, r, p]
| bit1 a, bit0 b :=
do let r := r.app_arg, (c, p) ← prove_add_nat c a b r, c.mk_app ``add_bit1_bit0 [a, b, r, p]
| bit1 a, bit1 b :=
do let r := r.app_arg, (c, p) ← prove_adc_nat c a b r, c.mk_app ``add_bit1_bit1 [a, b, r, p]
| _, _ := failed
end
with prove_adc_nat : instance_cache → expr → expr → expr → tactic (instance_cache × expr)
| c a b r := do
match match_numeral a, match_numeral b with
| zero, _ := do (c, p) ← prove_succ c b r, c.mk_app ``zero_adc [b, r, p]
| _, zero := do (c, p) ← prove_succ c b r, c.mk_app ``adc_zero [b, r, p]
| one, one := c.mk_app ``adc_one_one []
| bit0 a, one :=
do let r := r.app_arg, (c, p) ← prove_succ c a r, c.mk_app ``adc_bit0_one [a, r, p]
| one, bit0 b :=
do let r := r.app_arg, (c, p) ← prove_succ c b r, c.mk_app ``adc_one_bit0 [b, r, p]
| bit1 a, one :=
do let r := r.app_arg, (c, p) ← prove_succ c a r, c.mk_app ``adc_bit1_one [a, r, p]
| one, bit1 b :=
do let r := r.app_arg, (c, p) ← prove_succ c b r, c.mk_app ``adc_one_bit1 [b, r, p]
| bit0 a, bit0 b :=
do let r := r.app_arg, (c, p) ← prove_add_nat c a b r, c.mk_app ``adc_bit0_bit0 [a, b, r, p]
| bit0 a, bit1 b :=
do let r := r.app_arg, (c, p) ← prove_adc_nat c a b r, c.mk_app ``adc_bit0_bit1 [a, b, r, p]
| bit1 a, bit0 b :=
do let r := r.app_arg, (c, p) ← prove_adc_nat c a b r, c.mk_app ``adc_bit1_bit0 [a, b, r, p]
| bit1 a, bit1 b :=
do let r := r.app_arg, (c, p) ← prove_adc_nat c a b r, c.mk_app ``adc_bit1_bit1 [a, b, r, p]
| _, _ := failed
end
/-- Given `a`,`b`,`r` natural numerals, proves `⊢ a + b = r`. -/
add_decl_doc prove_add_nat
/-- Given `a`,`b`,`r` natural numerals, proves `⊢ a + b + 1 = r`. -/
add_decl_doc prove_adc_nat
/-- Given `a`,`b` natural numerals, returns `(r, ⊢ a + b = r)`. -/
meta def prove_add_nat' (c : instance_cache) (a b : expr) : tactic (instance_cache × expr × expr) :=
do na ← a.to_nat,
nb ← b.to_nat,
(c, r) ← c.of_nat (na + nb),
(c, p) ← prove_add_nat c a b r,
return (c, r, p)
end
theorem bit0_mul {α} [semiring α] (a b c : α) (h : a * b = c) :
bit0 a * b = bit0 c := h ▸ by simp [bit0, add_mul]
theorem mul_bit0' {α} [semiring α] (a b c : α) (h : a * b = c) :
a * bit0 b = bit0 c := h ▸ by simp [bit0, mul_add]
theorem mul_bit0_bit0 {α} [semiring α] (a b c : α) (h : a * b = c) :
bit0 a * bit0 b = bit0 (bit0 c) := bit0_mul _ _ _ (mul_bit0' _ _ _ h)
theorem mul_bit1_bit1 {α} [semiring α] (a b c d e : α)
(hc : a * b = c) (hd : a + b = d) (he : bit0 c + d = e) :
bit1 a * bit1 b = bit1 e :=
by rw [← he, ← hd, ← hc]; simp [bit1, bit0, mul_add, add_mul, add_left_comm, add_assoc]
section
open match_numeral_result
/-- Given `a`,`b` natural numerals, returns `(r, ⊢ a * b = r)`. -/
meta def prove_mul_nat : instance_cache → expr → expr → tactic (instance_cache × expr × expr)
| ic a b :=
match match_numeral a, match_numeral b with
| zero, _ := do
(ic, z) ← ic.mk_app ``has_zero.zero [],
(ic, p) ← ic.mk_app ``zero_mul [b],
return (ic, z, p)
| _, zero := do
(ic, z) ← ic.mk_app ``has_zero.zero [],
(ic, p) ← ic.mk_app ``mul_zero [a],
return (ic, z, p)
| one, _ := do (ic, p) ← ic.mk_app ``one_mul [b], return (ic, b, p)
| _, one := do (ic, p) ← ic.mk_app ``mul_one [a], return (ic, a, p)
| bit0 a, bit0 b := do
(ic, c, p) ← prove_mul_nat ic a b,
(ic, p) ← ic.mk_app ``mul_bit0_bit0 [a, b, c, p],
(ic, c') ← ic.mk_bit0 c,
(ic, c') ← ic.mk_bit0 c',
return (ic, c', p)
| bit0 a, _ := do
(ic, c, p) ← prove_mul_nat ic a b,
(ic, p) ← ic.mk_app ``bit0_mul [a, b, c, p],
(ic, c') ← ic.mk_bit0 c,
return (ic, c', p)
| _, bit0 b := do
(ic, c, p) ← prove_mul_nat ic a b,
(ic, p) ← ic.mk_app ``mul_bit0' [a, b, c, p],
(ic, c') ← ic.mk_bit0 c,
return (ic, c', p)
| bit1 a, bit1 b := do
(ic, c, pc) ← prove_mul_nat ic a b,
(ic, d, pd) ← prove_add_nat' ic a b,
(ic, c') ← ic.mk_bit0 c,
(ic, e, pe) ← prove_add_nat' ic c' d,
(ic, p) ← ic.mk_app ``mul_bit1_bit1 [a, b, c, d, e, pc, pd, pe],
(ic, e') ← ic.mk_bit1 e,
return (ic, e', p)
| _, _ := failed
end
end
lemma zero_lt_one [linear_ordered_semiring α] : (0 : α) < 1 := zero_lt_one
section
open match_numeral_result
/-- Given `a` a positive natural numeral, returns `⊢ 0 < a`. -/
meta def prove_pos_nat (c : instance_cache) : expr → tactic (instance_cache × expr)
| e :=
match match_numeral e with
| one := c.mk_app ``zero_lt_one []
| bit0 e := do (c, p) ← prove_pos_nat e, c.mk_app ``bit0_pos [e, p]
| bit1 e := do (c, p) ← prove_pos_nat e, c.mk_app ``bit1_pos' [e, p]
| _ := failed
end
end
/-- Given `a` a rational numeral, returns `⊢ 0 < a`. -/
meta def prove_pos (c : instance_cache) : expr → tactic (instance_cache × expr)
| `(%%e₁ / %%e₂) := do
(c, p₁) ← prove_pos_nat c e₁, (c, p₂) ← prove_pos_nat c e₂,
c.mk_app ``div_pos [e₁, e₂, p₁, p₂]
| e := prove_pos_nat c e
/-- `match_neg (- e) = some e`, otherwise `none` -/
meta def match_neg : expr → option expr
| `(- %%e) := some e
| _ := none
/-- `match_sign (- e) = inl e`, `match_sign 0 = inr ff`, otherwise `inr tt` -/
meta def match_sign : expr → expr ⊕ bool
| `(- %%e) := sum.inl e
| `(has_zero.zero) := sum.inr ff
| _ := sum.inr tt
theorem ne_zero_of_pos {α} [ordered_add_comm_group α] (a : α) : 0 < a → a ≠ 0 := ne_of_gt
theorem ne_zero_neg {α} [add_group α] (a : α) : a ≠ 0 → -a ≠ 0 := mt neg_eq_zero.1
/-- Given `a` a rational numeral, returns `⊢ a ≠ 0`. -/
meta def prove_ne_zero' (c : instance_cache) : expr → tactic (instance_cache × expr)
| a :=
match match_neg a with
| some a := do (c, p) ← prove_ne_zero' a, c.mk_app ``ne_zero_neg [a, p]
| none := do (c, p) ← prove_pos c a, c.mk_app ``ne_zero_of_pos [a, p]
end
theorem clear_denom_div {α} [division_ring α] (a b b' c d : α)
(h₀ : b ≠ 0) (h₁ : b * b' = d) (h₂ : a * b' = c) : (a / b) * d = c :=
by rwa [← h₁, ← mul_assoc, div_mul_cancel _ h₀]
/-- Given `a` nonnegative rational and `d` a natural number, returns `(b, ⊢ a * d = b)`.
(`d` should be a multiple of the denominator of `a`, so that `b` is a natural number.) -/
meta def prove_clear_denom'
(prove_ne_zero : instance_cache → expr → ℚ → tactic (instance_cache × expr))
(c : instance_cache) (a d : expr) (na : ℚ) (nd : ℕ) :
tactic (instance_cache × expr × expr) :=
if na.denom = 1 then
prove_mul_nat c a d
else do
[_, _, a, b] ← return a.get_app_args,
(c, b') ← c.of_nat (nd / na.denom),
(c, p₀) ← prove_ne_zero c b na.denom,
(c, _, p₁) ← prove_mul_nat c b b',
(c, r, p₂) ← prove_mul_nat c a b',
(c, p) ← c.mk_app ``clear_denom_div [a, b, b', r, d, p₀, p₁, p₂],
return (c, r, p)
theorem nonneg_pos {α} [ordered_cancel_add_comm_monoid α] (a : α) : 0 < a → 0 ≤ a := le_of_lt
theorem lt_one_bit0 {α} [linear_ordered_semiring α] (a : α) (h : 1 ≤ a) : 1 < bit0 a :=
lt_of_lt_of_le one_lt_two (bit0_le_bit0.2 h)
theorem lt_one_bit1 {α} [linear_ordered_semiring α] (a : α) (h : 0 < a) : 1 < bit1 a :=
one_lt_bit1.2 h
theorem lt_bit0_bit0 {α} [linear_ordered_semiring α] (a b : α) : a < b → bit0 a < bit0 b :=
bit0_lt_bit0.2
theorem lt_bit0_bit1 {α} [linear_ordered_semiring α] (a b : α) (h : a ≤ b) : bit0 a < bit1 b :=
lt_of_le_of_lt (bit0_le_bit0.2 h) (lt_add_one _)
theorem lt_bit1_bit0 {α} [linear_ordered_semiring α] (a b : α) (h : a + 1 ≤ b) : bit1 a < bit0 b :=
lt_of_lt_of_le (by simp [bit0, bit1, zero_lt_one, add_assoc]) (bit0_le_bit0.2 h)
theorem lt_bit1_bit1 {α} [linear_ordered_semiring α] (a b : α) : a < b → bit1 a < bit1 b :=
bit1_lt_bit1.2
theorem le_one_bit0 {α} [linear_ordered_semiring α] (a : α) (h : 1 ≤ a) : 1 ≤ bit0 a :=
le_of_lt (lt_one_bit0 _ h)
-- deliberately strong hypothesis because bit1 0 is not a numeral
theorem le_one_bit1 {α} [linear_ordered_semiring α] (a : α) (h : 0 < a) : 1 ≤ bit1 a :=
le_of_lt (lt_one_bit1 _ h)
theorem le_bit0_bit0 {α} [linear_ordered_semiring α] (a b : α) : a ≤ b → bit0 a ≤ bit0 b :=
bit0_le_bit0.2
theorem le_bit0_bit1 {α} [linear_ordered_semiring α] (a b : α) (h : a ≤ b) : bit0 a ≤ bit1 b :=
le_of_lt (lt_bit0_bit1 _ _ h)
theorem le_bit1_bit0 {α} [linear_ordered_semiring α] (a b : α) (h : a + 1 ≤ b) : bit1 a ≤ bit0 b :=
le_of_lt (lt_bit1_bit0 _ _ h)
theorem le_bit1_bit1 {α} [linear_ordered_semiring α] (a b : α) : a ≤ b → bit1 a ≤ bit1 b :=
bit1_le_bit1.2
theorem sle_one_bit0 {α} [linear_ordered_semiring α] (a : α) : 1 ≤ a → 1 + 1 ≤ bit0 a :=
bit0_le_bit0.2
theorem sle_one_bit1 {α} [linear_ordered_semiring α] (a : α) : 1 ≤ a → 1 + 1 ≤ bit1 a :=
le_bit0_bit1 _ _
theorem sle_bit0_bit0 {α} [linear_ordered_semiring α] (a b : α) : a + 1 ≤ b → bit0 a + 1 ≤ bit0 b :=
le_bit1_bit0 _ _
theorem sle_bit0_bit1 {α} [linear_ordered_semiring α] (a b : α) (h : a ≤ b) : bit0 a + 1 ≤ bit1 b :=
bit1_le_bit1.2 h
theorem sle_bit1_bit0 {α} [linear_ordered_semiring α] (a b : α) (h : a + 1 ≤ b) :
bit1 a + 1 ≤ bit0 b :=
(bit1_succ a _ rfl).symm ▸ bit0_le_bit0.2 h
theorem sle_bit1_bit1 {α} [linear_ordered_semiring α] (a b : α) (h : a + 1 ≤ b) :
bit1 a + 1 ≤ bit1 b :=
(bit1_succ a _ rfl).symm ▸ le_bit0_bit1 _ _ h
/-- Given `a` a rational numeral, returns `⊢ 0 ≤ a`. -/
meta def prove_nonneg (ic : instance_cache) : expr → tactic (instance_cache × expr)
| e@`(has_zero.zero) := ic.mk_app ``le_refl [e]
| e :=
if ic.α = `(ℕ) then
return (ic, `(nat.zero_le).mk_app [e])
else do
(ic, p) ← prove_pos ic e,
ic.mk_app ``nonneg_pos [e, p]
section
open match_numeral_result
/-- Given `a` a rational numeral, returns `⊢ 1 ≤ a`. -/
meta def prove_one_le_nat (ic : instance_cache) : expr → tactic (instance_cache × expr)
| a :=
match match_numeral a with
| one := ic.mk_app ``le_refl [a]
| bit0 a := do (ic, p) ← prove_one_le_nat a, ic.mk_app ``le_one_bit0 [a, p]
| bit1 a := do (ic, p) ← prove_pos_nat ic a, ic.mk_app ``le_one_bit1 [a, p]
| _ := failed
end
meta mutual def prove_le_nat, prove_sle_nat (ic : instance_cache)
with prove_le_nat : expr → expr → tactic (instance_cache × expr)
| a b :=
if a = b then ic.mk_app ``le_refl [a] else
match match_numeral a, match_numeral b with
| zero, _ := prove_nonneg ic b
| one, bit0 b := do (ic, p) ← prove_one_le_nat ic b, ic.mk_app ``le_one_bit0 [b, p]
| one, bit1 b := do (ic, p) ← prove_pos_nat ic b, ic.mk_app ``le_one_bit1 [b, p]
| bit0 a, bit0 b := do (ic, p) ← prove_le_nat a b, ic.mk_app ``le_bit0_bit0 [a, b, p]
| bit0 a, bit1 b := do (ic, p) ← prove_le_nat a b, ic.mk_app ``le_bit0_bit1 [a, b, p]
| bit1 a, bit0 b := do (ic, p) ← prove_sle_nat a b, ic.mk_app ``le_bit1_bit0 [a, b, p]
| bit1 a, bit1 b := do (ic, p) ← prove_le_nat a b, ic.mk_app ``le_bit1_bit1 [a, b, p]
| _, _ := failed
end
with prove_sle_nat : expr → expr → tactic (instance_cache × expr)
| a b :=
match match_numeral a, match_numeral b with
| zero, _ := prove_nonneg ic b
| one, bit0 b := do (ic, p) ← prove_one_le_nat ic b, ic.mk_app ``sle_one_bit0 [b, p]
| one, bit1 b := do (ic, p) ← prove_one_le_nat ic b, ic.mk_app ``sle_one_bit1 [b, p]
| bit0 a, bit0 b := do (ic, p) ← prove_sle_nat a b, ic.mk_app ``sle_bit0_bit0 [a, b, p]
| bit0 a, bit1 b := do (ic, p) ← prove_le_nat a b, ic.mk_app ``sle_bit0_bit1 [a, b, p]
| bit1 a, bit0 b := do (ic, p) ← prove_sle_nat a b, ic.mk_app ``sle_bit1_bit0 [a, b, p]
| bit1 a, bit1 b := do (ic, p) ← prove_sle_nat a b, ic.mk_app ``sle_bit1_bit1 [a, b, p]
| _, _ := failed
end
/-- Given `a`,`b` natural numerals, proves `⊢ a ≤ b`. -/
add_decl_doc prove_le_nat
/-- Given `a`,`b` natural numerals, proves `⊢ a + 1 ≤ b`. -/
add_decl_doc prove_sle_nat
/-- Given `a`,`b` natural numerals, proves `⊢ a < b`. -/
meta def prove_lt_nat (ic : instance_cache) : expr → expr → tactic (instance_cache × expr)
| a b :=
match match_numeral a, match_numeral b with
| zero, _ := prove_pos ic b
| one, bit0 b := do (ic, p) ← prove_one_le_nat ic b, ic.mk_app ``lt_one_bit0 [b, p]
| one, bit1 b := do (ic, p) ← prove_pos_nat ic b, ic.mk_app ``lt_one_bit1 [b, p]
| bit0 a, bit0 b := do (ic, p) ← prove_lt_nat a b, ic.mk_app ``lt_bit0_bit0 [a, b, p]
| bit0 a, bit1 b := do (ic, p) ← prove_le_nat ic a b, ic.mk_app ``lt_bit0_bit1 [a, b, p]
| bit1 a, bit0 b := do (ic, p) ← prove_sle_nat ic a b, ic.mk_app ``lt_bit1_bit0 [a, b, p]
| bit1 a, bit1 b := do (ic, p) ← prove_lt_nat a b, ic.mk_app ``lt_bit1_bit1 [a, b, p]
| _, _ := failed
end
end
theorem clear_denom_lt {α} [linear_ordered_semiring α] (a a' b b' d : α)
(h₀ : 0 < d) (ha : a * d = a') (hb : b * d = b') (h : a' < b') : a < b :=
lt_of_mul_lt_mul_right (by rwa [ha, hb]) (le_of_lt h₀)
/-- Given `a`,`b` nonnegative rational numerals, proves `⊢ a < b`. -/
meta def prove_lt_nonneg_rat (ic : instance_cache) (a b : expr) (na nb : ℚ) :
tactic (instance_cache × expr) :=
if na.denom = 1 ∧ nb.denom = 1 then
prove_lt_nat ic a b
else do
let nd := na.denom.lcm nb.denom,
(ic, d) ← ic.of_nat nd,
(ic, p₀) ← prove_pos ic d,
(ic, a', pa) ← prove_clear_denom' (λ ic e _, prove_ne_zero' ic e) ic a d na nd,
(ic, b', pb) ← prove_clear_denom' (λ ic e _, prove_ne_zero' ic e) ic b d nb nd,
(ic, p) ← prove_lt_nat ic a' b',
ic.mk_app ``clear_denom_lt [a, a', b, b', d, p₀, pa, pb, p]
lemma lt_neg_pos {α} [ordered_add_comm_group α] (a b : α) (ha : 0 < a) (hb : 0 < b) : -a < b :=
lt_trans (neg_neg_of_pos ha) hb
/-- Given `a`,`b` rational numerals, proves `⊢ a < b`. -/
meta def prove_lt_rat (ic : instance_cache) (a b : expr) (na nb : ℚ) :
tactic (instance_cache × expr) :=
match match_sign a, match_sign b with
| sum.inl a, sum.inl b := do
-- we have to switch the order of `a` and `b` because `a < b ↔ -b < -a`
(ic, p) ← prove_lt_nonneg_rat ic b a (-nb) (-na),
ic.mk_app ``neg_lt_neg [b, a, p]
| sum.inl a, sum.inr ff := do
(ic, p) ← prove_pos ic a,
ic.mk_app ``neg_neg_of_pos [a, p]
| sum.inl a, sum.inr tt := do
(ic, pa) ← prove_pos ic a,
(ic, pb) ← prove_pos ic b,
ic.mk_app ``lt_neg_pos [a, b, pa, pb]
| sum.inr ff, _ := prove_pos ic b
| sum.inr tt, _ := prove_lt_nonneg_rat ic a b na nb
end
theorem clear_denom_le {α} [linear_ordered_semiring α] (a a' b b' d : α)
(h₀ : 0 < d) (ha : a * d = a') (hb : b * d = b') (h : a' ≤ b') : a ≤ b :=
le_of_mul_le_mul_right (by rwa [ha, hb]) h₀
/-- Given `a`,`b` nonnegative rational numerals, proves `⊢ a ≤ b`. -/
meta def prove_le_nonneg_rat (ic : instance_cache) (a b : expr) (na nb : ℚ) :
tactic (instance_cache × expr) :=
if na.denom = 1 ∧ nb.denom = 1 then
prove_le_nat ic a b
else do
let nd := na.denom.lcm nb.denom,
(ic, d) ← ic.of_nat nd,
(ic, p₀) ← prove_pos ic d,
(ic, a', pa) ← prove_clear_denom' (λ ic e _, prove_ne_zero' ic e) ic a d na nd,
(ic, b', pb) ← prove_clear_denom' (λ ic e _, prove_ne_zero' ic e) ic b d nb nd,
(ic, p) ← prove_le_nat ic a' b',
ic.mk_app ``clear_denom_le [a, a', b, b', d, p₀, pa, pb, p]
lemma le_neg_pos {α} [ordered_add_comm_group α] (a b : α) (ha : 0 ≤ a) (hb : 0 ≤ b) : -a ≤ b :=
le_trans (neg_nonpos_of_nonneg ha) hb
/-- Given `a`,`b` rational numerals, proves `⊢ a ≤ b`. -/
meta def prove_le_rat (ic : instance_cache) (a b : expr) (na nb : ℚ) :
tactic (instance_cache × expr) :=
match match_sign a, match_sign b with
| sum.inl a, sum.inl b := do
(ic, p) ← prove_le_nonneg_rat ic a b (-na) (-nb),
ic.mk_app ``neg_le_neg [a, b, p]
| sum.inl a, sum.inr ff := do
(ic, p) ← prove_nonneg ic a,
ic.mk_app ``neg_nonpos_of_nonneg [a, p]
| sum.inl a, sum.inr tt := do
(ic, pa) ← prove_nonneg ic a,
(ic, pb) ← prove_nonneg ic b,
ic.mk_app ``le_neg_pos [a, b, pa, pb]
| sum.inr ff, _ := prove_nonneg ic b
| sum.inr tt, _ := prove_le_nonneg_rat ic a b na nb
end
/-- Given `a`,`b` rational numerals, proves `⊢ a ≠ b`. This version tries to prove
`⊢ a < b` or `⊢ b < a`, and so is not appropriate for types without an order relation. -/
meta def prove_ne_rat (ic : instance_cache) (a b : expr) (na nb : ℚ) :
tactic (instance_cache × expr) :=
if na < nb then do
(ic, p) ← prove_lt_rat ic a b na nb,
ic.mk_app ``ne_of_lt [a, b, p]
else do
(ic, p) ← prove_lt_rat ic b a nb na,
ic.mk_app ``ne_of_gt [a, b, p]
theorem nat_cast_zero {α} [semiring α] : ↑(0 : ℕ) = (0 : α) := nat.cast_zero
theorem nat_cast_one {α} [semiring α] : ↑(1 : ℕ) = (1 : α) := nat.cast_one
theorem nat_cast_bit0 {α} [semiring α] (a : ℕ) (a' : α) (h : ↑a = a') : ↑(bit0 a) = bit0 a' :=
h ▸ nat.cast_bit0 _
theorem nat_cast_bit1 {α} [semiring α] (a : ℕ) (a' : α) (h : ↑a = a') : ↑(bit1 a) = bit1 a' :=
h ▸ nat.cast_bit1 _
theorem int_cast_zero {α} [ring α] : ↑(0 : ℤ) = (0 : α) := int.cast_zero
theorem int_cast_one {α} [ring α] : ↑(1 : ℤ) = (1 : α) := int.cast_one
theorem int_cast_bit0 {α} [ring α] (a : ℤ) (a' : α) (h : ↑a = a') : ↑(bit0 a) = bit0 a' :=
h ▸ int.cast_bit0 _
theorem int_cast_bit1 {α} [ring α] (a : ℤ) (a' : α) (h : ↑a = a') : ↑(bit1 a) = bit1 a' :=
h ▸ int.cast_bit1 _
theorem rat_cast_bit0 {α} [division_ring α] [char_zero α] (a : ℚ) (a' : α) (h : ↑a = a') :
↑(bit0 a) = bit0 a' :=
h ▸ rat.cast_bit0 _
theorem rat_cast_bit1 {α} [division_ring α] [char_zero α] (a : ℚ) (a' : α) (h : ↑a = a') :
↑(bit1 a) = bit1 a' :=
h ▸ rat.cast_bit1 _
/-- Given `a' : α` a natural numeral, returns `(a : ℕ, ⊢ ↑a = a')`.
(Note that the returned value is on the left of the equality.) -/
meta def prove_nat_uncast (ic nc : instance_cache) : ∀ (a' : expr),
tactic (instance_cache × instance_cache × expr × expr)
| a' :=
match match_numeral a' with
| match_numeral_result.zero := do
(nc, e) ← nc.mk_app ``has_zero.zero [],
(ic, p) ← ic.mk_app ``nat_cast_zero [],
return (ic, nc, e, p)
| match_numeral_result.one := do
(nc, e) ← nc.mk_app ``has_one.one [],
(ic, p) ← ic.mk_app ``nat_cast_one [],
return (ic, nc, e, p)
| match_numeral_result.bit0 a' := do
(ic, nc, a, p) ← prove_nat_uncast a',
(nc, a0) ← nc.mk_bit0 a,
(ic, p) ← ic.mk_app ``nat_cast_bit0 [a, a', p],
return (ic, nc, a0, p)
| match_numeral_result.bit1 a' := do
(ic, nc, a, p) ← prove_nat_uncast a',
(nc, a1) ← nc.mk_bit1 a,
(ic, p) ← ic.mk_app ``nat_cast_bit1 [a, a', p],
return (ic, nc, a1, p)
| _ := failed
end
/-- Given `a' : α` a natural numeral, returns `(a : ℤ, ⊢ ↑a = a')`.
(Note that the returned value is on the left of the equality.) -/
meta def prove_int_uncast_nat (ic zc : instance_cache) : ∀ (a' : expr),
tactic (instance_cache × instance_cache × expr × expr)
| a' :=
match match_numeral a' with
| match_numeral_result.zero := do
(zc, e) ← zc.mk_app ``has_zero.zero [],
(ic, p) ← ic.mk_app ``int_cast_zero [],
return (ic, zc, e, p)
| match_numeral_result.one := do
(zc, e) ← zc.mk_app ``has_one.one [],
(ic, p) ← ic.mk_app ``int_cast_one [],
return (ic, zc, e, p)
| match_numeral_result.bit0 a' := do
(ic, zc, a, p) ← prove_int_uncast_nat a',
(zc, a0) ← zc.mk_bit0 a,
(ic, p) ← ic.mk_app ``int_cast_bit0 [a, a', p],
return (ic, zc, a0, p)
| match_numeral_result.bit1 a' := do
(ic, zc, a, p) ← prove_int_uncast_nat a',
(zc, a1) ← zc.mk_bit1 a,
(ic, p) ← ic.mk_app ``int_cast_bit1 [a, a', p],
return (ic, zc, a1, p)
| _ := failed
end
/-- Given `a' : α` a natural numeral, returns `(a : ℚ, ⊢ ↑a = a')`.
(Note that the returned value is on the left of the equality.) -/
meta def prove_rat_uncast_nat (ic qc : instance_cache) (cz_inst : expr) : ∀ (a' : expr),
tactic (instance_cache × instance_cache × expr × expr)
| a' :=
match match_numeral a' with
| match_numeral_result.zero := do
(qc, e) ← qc.mk_app ``has_zero.zero [],
(ic, p) ← ic.mk_app ``rat.cast_zero [],
return (ic, qc, e, p)
| match_numeral_result.one := do
(qc, e) ← qc.mk_app ``has_one.one [],
(ic, p) ← ic.mk_app ``rat.cast_one [],
return (ic, qc, e, p)
| match_numeral_result.bit0 a' := do
(ic, qc, a, p) ← prove_rat_uncast_nat a',
(qc, a0) ← qc.mk_bit0 a,
(ic, p) ← ic.mk_app ``rat_cast_bit0 [cz_inst, a, a', p],
return (ic, qc, a0, p)
| match_numeral_result.bit1 a' := do
(ic, qc, a, p) ← prove_rat_uncast_nat a',
(qc, a1) ← qc.mk_bit1 a,
(ic, p) ← ic.mk_app ``rat_cast_bit1 [cz_inst, a, a', p],
return (ic, qc, a1, p)
| _ := failed
end
theorem rat_cast_div {α} [division_ring α] [char_zero α] (a b : ℚ) (a' b' : α)
(ha : ↑a = a') (hb : ↑b = b') : ↑(a / b) = a' / b' :=
ha ▸ hb ▸ rat.cast_div _ _
/-- Given `a' : α` a nonnegative rational numeral, returns `(a : ℚ, ⊢ ↑a = a')`.
(Note that the returned value is on the left of the equality.) -/
meta def prove_rat_uncast_nonneg (ic qc : instance_cache) (cz_inst a' : expr) (na' : ℚ) :
tactic (instance_cache × instance_cache × expr × expr) :=
if na'.denom = 1 then
prove_rat_uncast_nat ic qc cz_inst a'
else do
[_, _, a', b'] ← return a'.get_app_args,
(ic, qc, a, pa) ← prove_rat_uncast_nat ic qc cz_inst a',
(ic, qc, b, pb) ← prove_rat_uncast_nat ic qc cz_inst b',
(qc, e) ← qc.mk_app ``has_div.div [a, b],
(ic, p) ← ic.mk_app ``rat_cast_div [cz_inst, a, b, a', b', pa, pb],
return (ic, qc, e, p)
theorem int_cast_neg {α} [ring α] (a : ℤ) (a' : α) (h : ↑a = a') : ↑-a = -a' :=
h ▸ int.cast_neg _
theorem rat_cast_neg {α} [division_ring α] (a : ℚ) (a' : α) (h : ↑a = a') : ↑-a = -a' :=
h ▸ rat.cast_neg _
/-- Given `a' : α` an integer numeral, returns `(a : ℤ, ⊢ ↑a = a')`.
(Note that the returned value is on the left of the equality.) -/
meta def prove_int_uncast (ic zc : instance_cache) (a' : expr) :
tactic (instance_cache × instance_cache × expr × expr) :=
match match_neg a' with
| some a' := do
(ic, zc, a, p) ← prove_int_uncast_nat ic zc a',
(zc, e) ← zc.mk_app ``has_neg.neg [a],
(ic, p) ← ic.mk_app ``int_cast_neg [a, a', p],
return (ic, zc, e, p)
| none := prove_int_uncast_nat ic zc a'
end
/-- Given `a' : α` a rational numeral, returns `(a : ℚ, ⊢ ↑a = a')`.
(Note that the returned value is on the left of the equality.) -/
meta def prove_rat_uncast (ic qc : instance_cache) (cz_inst a' : expr) (na' : ℚ) :
tactic (instance_cache × instance_cache × expr × expr) :=
match match_neg a' with
| some a' := do
(ic, qc, a, p) ← prove_rat_uncast_nonneg ic qc cz_inst a' (-na'),
(qc, e) ← qc.mk_app ``has_neg.neg [a],
(ic, p) ← ic.mk_app ``rat_cast_neg [a, a', p],
return (ic, qc, e, p)
| none := prove_rat_uncast_nonneg ic qc cz_inst a' na'
end
theorem nat_cast_ne {α} [semiring α] [char_zero α] (a b : ℕ) (a' b' : α)
(ha : ↑a = a') (hb : ↑b = b') (h : a ≠ b) : a' ≠ b' :=
ha ▸ hb ▸ mt nat.cast_inj.1 h
theorem int_cast_ne {α} [ring α] [char_zero α] (a b : ℤ) (a' b' : α)
(ha : ↑a = a') (hb : ↑b = b') (h : a ≠ b) : a' ≠ b' :=
ha ▸ hb ▸ mt int.cast_inj.1 h
theorem rat_cast_ne {α} [division_ring α] [char_zero α] (a b : ℚ) (a' b' : α)
(ha : ↑a = a') (hb : ↑b = b') (h : a ≠ b) : a' ≠ b' :=
ha ▸ hb ▸ mt rat.cast_inj.1 h
/-- Given `a`,`b` rational numerals, proves `⊢ a ≠ b`. Currently it tries two methods:
* Prove `⊢ a < b` or `⊢ b < a`, if the base type has an order
* Embed `↑(a':ℚ) = a` and `↑(b':ℚ) = b`, and then prove `a' ≠ b'`.
This requires that the base type be `char_zero`, and also that it be a `division_ring`
so that the coercion from `ℚ` is well defined.
We may also add coercions to `ℤ` and `ℕ` as well in order to support `char_zero`
rings and semirings. -/
meta def prove_ne : instance_cache → expr → expr → ℚ → ℚ → tactic (instance_cache × expr)
| ic a b na nb := prove_ne_rat ic a b na nb <|> do
cz_inst ← mk_mapp ``char_zero [ic.α, none] >>= mk_instance,
if na.denom = 1 ∧ nb.denom = 1 then
if na ≥ 0 ∧ nb ≥ 0 then do
guard (ic.α ≠ `(ℕ)),
nc ← mk_instance_cache `(ℕ),
(ic, nc, a', pa) ← prove_nat_uncast ic nc a,
(ic, nc, b', pb) ← prove_nat_uncast ic nc b,
(nc, p) ← prove_ne_rat nc a' b' na nb,
ic.mk_app ``nat_cast_ne [cz_inst, a', b', a, b, pa, pb, p]
else do
guard (ic.α ≠ `(ℤ)),
zc ← mk_instance_cache `(ℤ),
(ic, zc, a', pa) ← prove_int_uncast ic zc a,
(ic, zc, b', pb) ← prove_int_uncast ic zc b,
(zc, p) ← prove_ne_rat zc a' b' na nb,
ic.mk_app ``int_cast_ne [cz_inst, a', b', a, b, pa, pb, p]
else do
guard (ic.α ≠ `(ℚ)),
qc ← mk_instance_cache `(ℚ),
(ic, qc, a', pa) ← prove_rat_uncast ic qc cz_inst a na,
(ic, qc, b', pb) ← prove_rat_uncast ic qc cz_inst b nb,
(qc, p) ← prove_ne_rat qc a' b' na nb,
ic.mk_app ``rat_cast_ne [cz_inst, a', b', a, b, pa, pb, p]
/-- Given `a` a rational numeral, returns `⊢ a ≠ 0`. -/
meta def prove_ne_zero (ic : instance_cache) : expr → ℚ → tactic (instance_cache × expr)
| a na := do
(ic, z) ← ic.mk_app ``has_zero.zero [],
prove_ne ic a z na 0
/-- Given `a` nonnegative rational and `d` a natural number, returns `(b, ⊢ a * d = b)`.
(`d` should be a multiple of the denominator of `a`, so that `b` is a natural number.) -/
meta def prove_clear_denom : instance_cache → expr → expr → ℚ → ℕ →
tactic (instance_cache × expr × expr) := prove_clear_denom' prove_ne_zero
theorem clear_denom_add {α} [division_ring α] (a a' b b' c c' d : α)
(h₀ : d ≠ 0) (ha : a * d = a') (hb : b * d = b') (hc : c * d = c')
(h : a' + b' = c') : a + b = c :=
mul_right_cancel₀ h₀ $ by rwa [add_mul, ha, hb, hc]
/-- Given `a`,`b`,`c` nonnegative rational numerals, returns `⊢ a + b = c`. -/
meta def prove_add_nonneg_rat (ic : instance_cache) (a b c : expr) (na nb nc : ℚ) :
tactic (instance_cache × expr) :=
if na.denom = 1 ∧ nb.denom = 1 then
prove_add_nat ic a b c
else do
let nd := na.denom.lcm nb.denom,
(ic, d) ← ic.of_nat nd,
(ic, p₀) ← prove_ne_zero ic d nd,
(ic, a', pa) ← prove_clear_denom ic a d na nd,
(ic, b', pb) ← prove_clear_denom ic b d nb nd,
(ic, c', pc) ← prove_clear_denom ic c d nc nd,
(ic, p) ← prove_add_nat ic a' b' c',
ic.mk_app ``clear_denom_add [a, a', b, b', c, c', d, p₀, pa, pb, pc, p]
theorem add_pos_neg_pos {α} [add_group α] (a b c : α) (h : c + b = a) : a + -b = c :=
h ▸ by simp
theorem add_pos_neg_neg {α} [add_group α] (a b c : α) (h : c + a = b) : a + -b = -c :=
h ▸ by simp
theorem add_neg_pos_pos {α} [add_group α] (a b c : α) (h : a + c = b) : -a + b = c :=
h ▸ by simp
theorem add_neg_pos_neg {α} [add_group α] (a b c : α) (h : b + c = a) : -a + b = -c :=
h ▸ by simp
theorem add_neg_neg {α} [add_group α] (a b c : α) (h : b + a = c) : -a + -b = -c :=
h ▸ by simp
/-- Given `a`,`b`,`c` rational numerals, returns `⊢ a + b = c`. -/
meta def prove_add_rat (ic : instance_cache) (ea eb ec : expr) (a b c : ℚ) :
tactic (instance_cache × expr) :=
match match_neg ea, match_neg eb, match_neg ec with
| some ea, some eb, some ec := do
(ic, p) ← prove_add_nonneg_rat ic eb ea ec (-b) (-a) (-c),
ic.mk_app ``add_neg_neg [ea, eb, ec, p]
| some ea, none, some ec := do
(ic, p) ← prove_add_nonneg_rat ic eb ec ea b (-c) (-a),
ic.mk_app ``add_neg_pos_neg [ea, eb, ec, p]
| some ea, none, none := do
(ic, p) ← prove_add_nonneg_rat ic ea ec eb (-a) c b,
ic.mk_app ``add_neg_pos_pos [ea, eb, ec, p]
| none, some eb, some ec := do
(ic, p) ← prove_add_nonneg_rat ic ec ea eb (-c) a (-b),
ic.mk_app ``add_pos_neg_neg [ea, eb, ec, p]
| none, some eb, none := do
(ic, p) ← prove_add_nonneg_rat ic ec eb ea c (-b) a,
ic.mk_app ``add_pos_neg_pos [ea, eb, ec, p]
| _, _, _ := prove_add_nonneg_rat ic ea eb ec a b c
end
/-- Given `a`,`b` rational numerals, returns `(c, ⊢ a + b = c)`. -/
meta def prove_add_rat' (ic : instance_cache) (a b : expr) :
tactic (instance_cache × expr × expr) :=
do na ← a.to_rat,
nb ← b.to_rat,
let nc := na + nb,
(ic, c) ← ic.of_rat nc,
(ic, p) ← prove_add_rat ic a b c na nb nc,
return (ic, c, p)
theorem clear_denom_simple_nat {α} [division_ring α] (a : α) :
(1:α) ≠ 0 ∧ a * 1 = a := ⟨one_ne_zero, mul_one _⟩
theorem clear_denom_simple_div {α} [division_ring α] (a b : α) (h : b ≠ 0) :
b ≠ 0 ∧ a / b * b = a := ⟨h, div_mul_cancel _ h⟩
/-- Given `a` a nonnegative rational numeral, returns `(b, c, ⊢ a * b = c)`
where `b` and `c` are natural numerals. (`b` will be the denominator of `a`.) -/
meta def prove_clear_denom_simple (c : instance_cache) (a : expr) (na : ℚ) :
tactic (instance_cache × expr × expr × expr) :=
if na.denom = 1 then do
(c, d) ← c.mk_app ``has_one.one [],
(c, p) ← c.mk_app ``clear_denom_simple_nat [a],
return (c, d, a, p)
else do
[α, _, a, b] ← return a.get_app_args,
(c, p₀) ← prove_ne_zero c b na.denom,
(c, p) ← c.mk_app ``clear_denom_simple_div [a, b, p₀],
return (c, b, a, p)
theorem clear_denom_mul {α} [field α] (a a' b b' c c' d₁ d₂ d : α)
(ha : d₁ ≠ 0 ∧ a * d₁ = a') (hb : d₂ ≠ 0 ∧ b * d₂ = b')
(hc : c * d = c') (hd : d₁ * d₂ = d)
(h : a' * b' = c') : a * b = c :=
mul_right_cancel₀ ha.1 $ mul_right_cancel₀ hb.1 $
by rw [mul_assoc c, hd, hc, ← h, ← ha.2, ← hb.2, ← mul_assoc, mul_right_comm a]
/-- Given `a`,`b` nonnegative rational numerals, returns `(c, ⊢ a * b = c)`. -/
meta def prove_mul_nonneg_rat (ic : instance_cache) (a b : expr) (na nb : ℚ) :
tactic (instance_cache × expr × expr) :=
if na.denom = 1 ∧ nb.denom = 1 then
prove_mul_nat ic a b
else do
let nc := na * nb, (ic, c) ← ic.of_rat nc,
(ic, d₁, a', pa) ← prove_clear_denom_simple ic a na,
(ic, d₂, b', pb) ← prove_clear_denom_simple ic b nb,
(ic, d, pd) ← prove_mul_nat ic d₁ d₂, nd ← d.to_nat,
(ic, c', pc) ← prove_clear_denom ic c d nc nd,
(ic, _, p) ← prove_mul_nat ic a' b',
(ic, p) ← ic.mk_app ``clear_denom_mul [a, a', b, b', c, c', d₁, d₂, d, pa, pb, pc, pd, p],
return (ic, c, p)
theorem mul_neg_pos {α} [ring α] (a b c : α) (h : a * b = c) : -a * b = -c := h ▸ by simp
theorem mul_pos_neg {α} [ring α] (a b c : α) (h : a * b = c) : a * -b = -c := h ▸ by simp
theorem mul_neg_neg {α} [ring α] (a b c : α) (h : a * b = c) : -a * -b = c := h ▸ by simp
/-- Given `a`,`b` rational numerals, returns `(c, ⊢ a * b = c)`. -/
meta def prove_mul_rat (ic : instance_cache) (a b : expr) (na nb : ℚ) :
tactic (instance_cache × expr × expr) :=
match match_sign a, match_sign b with
| sum.inl a, sum.inl b := do
(ic, c, p) ← prove_mul_nonneg_rat ic a b (-na) (-nb),
(ic, p) ← ic.mk_app ``mul_neg_neg [a, b, c, p],
return (ic, c, p)
| sum.inr ff, _ := do
(ic, z) ← ic.mk_app ``has_zero.zero [],
(ic, p) ← ic.mk_app ``zero_mul [b],
return (ic, z, p)
| _, sum.inr ff := do
(ic, z) ← ic.mk_app ``has_zero.zero [],
(ic, p) ← ic.mk_app ``mul_zero [a],
return (ic, z, p)
| sum.inl a, sum.inr tt := do
(ic, c, p) ← prove_mul_nonneg_rat ic a b (-na) nb,
(ic, p) ← ic.mk_app ``mul_neg_pos [a, b, c, p],
(ic, c') ← ic.mk_app ``has_neg.neg [c],
return (ic, c', p)
| sum.inr tt, sum.inl b := do
(ic, c, p) ← prove_mul_nonneg_rat ic a b na (-nb),
(ic, p) ← ic.mk_app ``mul_pos_neg [a, b, c, p],
(ic, c') ← ic.mk_app ``has_neg.neg [c],
return (ic, c', p)
| sum.inr tt, sum.inr tt := prove_mul_nonneg_rat ic a b na nb
end
theorem inv_neg {α} [division_ring α] (a b : α) (h : a⁻¹ = b) : (-a)⁻¹ = -b :=
h ▸ by simp only [inv_eq_one_div, one_div_neg_eq_neg_one_div]
theorem inv_one {α} [division_ring α] : (1 : α)⁻¹ = 1 := inv_one
theorem inv_one_div {α} [division_ring α] (a : α) : (1 / a)⁻¹ = a :=
by rw [one_div, inv_inv]
theorem inv_div_one {α} [division_ring α] (a : α) : a⁻¹ = 1 / a :=
inv_eq_one_div _
theorem inv_div {α} [division_ring α] (a b : α) : (a / b)⁻¹ = b / a :=
by simp only [inv_eq_one_div, one_div_div]
/-- Given `a` a rational numeral, returns `(b, ⊢ a⁻¹ = b)`. -/
meta def prove_inv : instance_cache → expr → ℚ → tactic (instance_cache × expr × expr)
| ic e n :=
match match_sign e with
| sum.inl e := do
(ic, e', p) ← prove_inv ic e (-n),
(ic, r) ← ic.mk_app ``has_neg.neg [e'],
(ic, p) ← ic.mk_app ``inv_neg [e, e', p],
return (ic, r, p)
| sum.inr ff := do
(ic, p) ← ic.mk_app ``inv_zero [],
return (ic, e, p)
| sum.inr tt :=
if n.num = 1 then
if n.denom = 1 then do
(ic, p) ← ic.mk_app ``inv_one [],
return (ic, e, p)
else do
let e := e.app_arg,
(ic, p) ← ic.mk_app ``inv_one_div [e],
return (ic, e, p)
else if n.denom = 1 then do
(ic, p) ← ic.mk_app ``inv_div_one [e],
e ← infer_type p,
return (ic, e.app_arg, p)
else do
[_, _, a, b] ← return e.get_app_args,
(ic, e') ← ic.mk_app ``has_div.div [b, a],
(ic, p) ← ic.mk_app ``inv_div [a, b],
return (ic, e', p)
end
theorem div_eq {α} [division_ring α] (a b b' c : α)
(hb : b⁻¹ = b') (h : a * b' = c) : a / b = c :=
by rwa [ ← hb, ← div_eq_mul_inv] at h
/-- Given `a`,`b` rational numerals, returns `(c, ⊢ a / b = c)`. -/
meta def prove_div (ic : instance_cache) (a b : expr) (na nb : ℚ) :
tactic (instance_cache × expr × expr) :=
do (ic, b', pb) ← prove_inv ic b nb,
(ic, c, p) ← prove_mul_rat ic a b' na nb⁻¹,
(ic, p) ← ic.mk_app ``div_eq [a, b, b', c, pb, p],
return (ic, c, p)
/-- Given `a` a rational numeral, returns `(b, ⊢ -a = b)`. -/
meta def prove_neg (ic : instance_cache) (a : expr) : tactic (instance_cache × expr × expr) :=
match match_sign a with
| sum.inl a := do
(ic, p) ← ic.mk_app ``neg_neg [a],
return (ic, a, p)
| sum.inr ff := do
(ic, p) ← ic.mk_app ``neg_zero [],
return (ic, a, p)
| sum.inr tt := do
(ic, a') ← ic.mk_app ``has_neg.neg [a],
p ← mk_eq_refl a',
return (ic, a', p)
end
theorem sub_pos {α} [add_group α] (a b b' c : α) (hb : -b = b') (h : a + b' = c) : a - b = c :=
by rwa [← hb, ← sub_eq_add_neg] at h
theorem sub_neg {α} [add_group α] (a b c : α) (h : a + b = c) : a - -b = c :=
by rwa sub_neg_eq_add
/-- Given `a`,`b` rational numerals, returns `(c, ⊢ a - b = c)`. -/
meta def prove_sub (ic : instance_cache) (a b : expr) : tactic (instance_cache × expr × expr) :=
match match_sign b with
| sum.inl b := do
(ic, c, p) ← prove_add_rat' ic a b,
(ic, p) ← ic.mk_app ``sub_neg [a, b, c, p],
return (ic, c, p)
| sum.inr ff := do
(ic, p) ← ic.mk_app ``sub_zero [a],
return (ic, a, p)
| sum.inr tt := do
(ic, b', pb) ← prove_neg ic b,
(ic, c, p) ← prove_add_rat' ic a b',
(ic, p) ← ic.mk_app ``sub_pos [a, b, b', c, pb, p],
return (ic, c, p)
end
theorem sub_nat_pos (a b c : ℕ) (h : b + c = a) : a - b = c :=
h ▸ add_tsub_cancel_left _ _
theorem sub_nat_neg (a b c : ℕ) (h : a + c = b) : a - b = 0 :=
tsub_eq_zero_iff_le.mpr $ h ▸ nat.le_add_right _ _
/-- Given `a : nat`,`b : nat` natural numerals, returns `(c, ⊢ a - b = c)`. -/
meta def prove_sub_nat (ic : instance_cache) (a b : expr) : tactic (expr × expr) :=
do na ← a.to_nat, nb ← b.to_nat,
if nb ≤ na then do
(ic, c) ← ic.of_nat (na - nb),
(ic, p) ← prove_add_nat ic b c a,
return (c, `(sub_nat_pos).mk_app [a, b, c, p])
else do
(ic, c) ← ic.of_nat (nb - na),
(ic, p) ← prove_add_nat ic a c b,
return (`(0 : ℕ), `(sub_nat_neg).mk_app [a, b, c, p])
/-- Evaluates the basic field operations `+`,`neg`,`-`,`*`,`inv`,`/` on numerals.
Also handles nat subtraction. Does not do recursive simplification; that is,
`1 + 1 + 1` will not simplify but `2 + 1` will. This is handled by the top level
`simp` call in `norm_num.derive`. -/
meta def eval_field : expr → tactic (expr × expr)
| `(%%e₁ + %%e₂) := do
n₁ ← e₁.to_rat, n₂ ← e₂.to_rat,
c ← infer_type e₁ >>= mk_instance_cache,
let n₃ := n₁ + n₂,
(c, e₃) ← c.of_rat n₃,
(_, p) ← prove_add_rat c e₁ e₂ e₃ n₁ n₂ n₃,
return (e₃, p)
| `(%%e₁ * %%e₂) := do
n₁ ← e₁.to_rat, n₂ ← e₂.to_rat,
c ← infer_type e₁ >>= mk_instance_cache,
prod.snd <$> prove_mul_rat c e₁ e₂ n₁ n₂
| `(- %%e) := do
c ← infer_type e >>= mk_instance_cache,
prod.snd <$> prove_neg c e
| `(@has_sub.sub %%α %%inst %%a %%b) := do
c ← mk_instance_cache α,
if α = `(nat) then prove_sub_nat c a b
else prod.snd <$> prove_sub c a b
| `(has_inv.inv %%e) := do