norm_num #
Evaluating arithmetic expressions including *, +, -, ^, ≤.
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.
An attribute for adding additional extensions to norm_num. To use this attribute, put
@[norm_num] on a tactic of type expr → tactic (expr × expr); the tactic will be called on
subterms by norm_num, and it is responsible for identifying that the expression is a numerical
function applied to numerals, for example nat.fib 17, and should return the reduced numerical
expression (which must be in norm_num-normal form: a natural or rational numeral, i.e. 37,
12 / 7 or -(2 / 3), although this can be an expression in any type), and the proof that the
original expression is equal to the rewritten expression.
Failure is used to indicate that this tactic does not apply to the term. For performance reasons, it is best to detect non-applicability as soon as possible so that the next tactic can have a go, so generally it will start with a pattern match and then checking that the arguments to the term are numerals or of the appropriate form, followed by proof construction, which should not fail.
Propositions are treated like any other term. The normal form for propositions is true or
false, so it should produce a proof of the form p = true or p = false. eq_true_intro can be
used to help here.
Normalises numerical expressions. It supports the operations + - * / ^ and % over
numerical types such as ℕ, ℤ, ℚ, ℝ, ℂ, and can prove goals of the form A = B, A ≠ B,
A < B and A ≤ B, where A and B are numerical expressions.
Add-on tactics marked as @[norm_num] can extend the behavior of norm_num to include other
functions. This is used to support several other functions on nat like prime, min_fac and
factors.
import data.real.basic
example : (2 : ℝ) + 2 = 4 := by norm_num
example : (12345.2 : ℝ) ≠ 12345.3 := by norm_num
example : (73 : ℝ) < 789/2 := by norm_num
example : 123456789 + 987654321 = 1111111110 := by norm_num
example (R : Type*) [ring R] : (2 : R) + 2 = 4 := by norm_num
example (F : Type*) [linear_ordered_field F] : (2 : F) + 2 < 5 := by norm_num
example : nat.prime (2^13 - 1) := by norm_num
example : ¬ nat.prime (2^11 - 1) := by norm_num
example (x : ℝ) (h : x = 123 + 456) : x = 579 := by norm_num at h; assumption
The variant norm_num1 does not call simp.
Both norm_num and norm_num1 can be called inside the conv tactic.
The tactic apply_normed normalises a numerical expression and tries to close the goal with
the result. Compare:
def a : ℕ := 2^100
#print a -- 2 ^ 100
def normed_a : ℕ := by apply_normed 2^100
#print normed_a -- 1267650600228229401496703205376
```
#norm_num command #
A user command to run norm_num. Mostly copied from the #simp command.
The basic usage is #norm_num e, where e is an expression,
which will print the norm_num form of e.
Syntax: #norm_num (only)? ([ simp lemma list ])? (with simp sets)? :? expression
This accepts the same options as the #simp command.
You can specify additional simp lemmas as usual, for example using
#norm_num [f, g] : e, or #norm_num with attr : e.
(The colon is optional but helpful for the parser.)
The only restricts norm_num to using only the provided lemmas, and so
#norm_num only : e behaves similarly to norm_num1.
Unlike norm_num, this command does not fail when no simplifications are made.
#norm_num understands local variables, so you can use them to
introduce parameters.