Mirror of https://github.com/leanprover/lean2 in case it ever disappears
04eaf184a9
@avigad, @fpvandoorn, @rlewis1988, @dselsam
This commit modifies how have-expressions are elaborated.
Now, to process
have H : <type>, from <proof>,
<rest>
we first process the constraints in <type> and <proof> simultaneously.
After all these constraints are solved, the elaborator performs
a Prolog-like cut, and process the constraints in <rest>.
So, all overloads, type classes and coercions in <type> and <proof> are solved
before we start processing <rest>. Moreover, while processing <rest>, we
cannot backtrack to <type> and <proof> anymore.
I fixed all affected proofs in the standard and HoTT libraries in
previous commits pushed today and yesterday. I think most affected proofs were not using a good
style and/or were easy to fix. Here is a common pattern that does not
work anymore.
structure has_scalar [class] (F V : Type) :=
(smul : F → V → V)
infixl ` • `:73 := has_scalar.smul
proposition smul_zero (a : R) : a • (0 : M) = 0 :=
have a • 0 + a • 0 = a • 0 + 0, by rewrite [-smul_left_distrib, *add_zero],
!add.left_cancel this
The `have` doesn't work because Lean can't figure out the type of 0 before
it starts processing `!add.left_cancel this`. This is easy to fix, we just have to
annotate one of the `0`s in the `have`:
proposition smul_zero (a : R) : a • (0 : M) = 0 :=
have a • (0:M) + a • 0 = a • 0 + 0, by rewrite [-smul_left_distrib, *add_zero],
!add.left_cancel this
BTW, all tactics are still being executed after all constraints are solved.
We may change that in the future. I didn't want to execute
the tactics at <proof> before <rest> because of universe
meta-variables. In Lean, unassigned universe meta-variables become
parameters. Moreover, we perform this conversion *before*
we start processing tactics. Reason: universe meta-variables
create many problems for tactics such as `rewrite`, `blast` and `simp`.
Finally, we can recover the previous behavior using the option
set_option parser.checkpoint_have false
|
||
|---|---|---|
| bin | ||
| doc | ||
| extras | ||
| hott | ||
| images | ||
| library | ||
| script | ||
| src | ||
| tests | ||
| .gitignore | ||
| .travis.osx.yml | ||
| .travis.windows.yml | ||
| .travis.yml | ||
| LICENSE | ||
| README.md | ||
| License | Windows | Ubuntu | OS X | Builds/Tests |
|---|---|---|---|---|
 |
 |
 |
 |
 |
About
- Homepage
- Theorem Proving in Lean: HTML, PDF
- Authors
- Standard Library
- HoTT Library
- Short Tutorial
- To Do list
Requirements
- C++11 compatible compiler: g++ (version >= 4.8.1), or clang++ (version >= 3.3)
- CMake
- GMP (GNU multiprecision library)
- MPFR (GNU MPFR Library)
- Lua 5.2 or 5.1, or LuaJIT 2.0
- (optional) gperftools
- (optional) Boost (version >= 1.54), we can build Lean using boost::thread instead of std::thread. When using Boost, Lean can modify the thread stack size.
Installing required packages at
Windows
Linux
OS X
Build Instructions
Miscellaneous
- Testing and Code Coverage
- Building Doxygen Documentation:
doxygen src/Doxyfile - Coding Style
- Library Style Conventions
- Git Commit Conventions
- Automatic Builds
- Syntax Highlight Lean Code in LaTeX