Commit graph

643 commits

Author SHA1 Message Date
Leonardo de Moura
6417c79569 feat(kernel/environment): add is_descendant method
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-21 14:28:50 -07:00
Leonardo de Moura
bfeb51ce58 feat(kernel/environment): add trust level field
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-21 13:39:47 -07:00
Leonardo de Moura
ee58a83e25 chore(kernel): remove unnecessary files
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-18 14:25:09 -07:00
Leonardo de Moura
d0dc16355b chore(kernel): remove unnecessary file
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-18 14:23:32 -07:00
Leonardo de Moura
582352d647 refactor(kernel/environment): simplified (functional) environment object
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-18 14:21:49 -07:00
Leonardo de Moura
234abb1238 feat(kernel/definition): default constructor for definitions
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-18 13:10:05 -07:00
Leonardo de Moura
984ac03ac7 refactor(kernel): replace kernel object with definition, disable affected files
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-17 16:10:47 -07:00
Leonardo de Moura
cb479a75ae fix(kernel/expr): make sure we cannot create a free variable with index uint_max, reason: get_free_var_range would return an incorrect value
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-17 13:25:21 -07:00
Leonardo de Moura
3712da0b54 refactor(kernel/instantiate): use get_free_var_range to improve instantiate, remove instantiate_with_closed, fix index overflow bug
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-17 13:12:49 -07:00
Leonardo de Moura
1fd5e9682d refactor(kernel/free_vars): use get_free_var_range to improve lift_free_vars and lower_free_vars performance
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-17 12:41:06 -07:00
Leonardo de Moura
4ae958af56 refactor(kernel/free_vars): use get_free_var_range to improve has_free_var_in_range performance
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-17 12:18:19 -07:00
Leonardo de Moura
dc864bf7b9 feat(kernel): store free variable range in composite expressions
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-17 11:31:48 -07:00
Leonardo de Moura
bc8379256a refactor(kernel): remove pairs from kernel
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-04-17 10:52:07 -07:00
Leonardo de Moura
fb2ec8fb12 fix(kernel): style
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:57 -07:00
Leonardo de Moura
9b161b825f refactor(kernel): instantiate_params
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:57 -07:00
Leonardo de Moura
3651b4ecd0 refactor(kernel): replace_fn functional object
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:57 -07:00
Leonardo de Moura
3939b93c2d refactor(kernel): substitution
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:57 -07:00
Leonardo de Moura
25948ac534 refactor(kernel): cleanup interfaces
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:57 -07:00
Leonardo de Moura
08087ea9c6 refactor(kernel): remove dead code
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:57 -07:00
Leonardo de Moura
eb487e44c1 refactor(kernel): use names instead of unsigned integers to encode level parameters
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:57 -07:00
Leonardo de Moura
ddbb3a7944 refactor(kernel): add error msg formatters, remove unnecessary files, add new type_checker interface
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:57 -07:00
Leonardo de Moura
916301bdfb refactor(kernel): parametric kernel objects
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:57 -07:00
Leonardo de Moura
54801bbd05 refactor(kernel): constraints
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:57 -07:00
Leonardo de Moura
aa4a7acccf feat(kernel/level): is_trivial predicate for level constraints
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:57 -07:00
Leonardo de Moura
4b7fe064fe refactor(kernel): finish formatter interface
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
bf13441bd7 fix(kernel): bugs in justification module, add missing metavar methods, add basic metavar tests
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
4c30ea9251 fix(kernel/justification): none is the unit of mk_composite
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
3c6002e969 refactor(kernel): add mk_rev_app, update_rev_app, implement instantiate_metavars functions, modify instantiate (free vars) API
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
42e253c962 fix(*): style and clang warnings
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
968c0d799f refactor(kernel): implement substitution methods
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
5f4b1cf47e feat(kernel): define metavar substitution based on red-black trees
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
fdde12e6af refactor(kernel): remove unnecessary files
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
2a73389ed3 refactor(kernel): justification objects
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
501435f6fc feat(kernel): add has_local predicate
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
997f32378c refactor(kernel): remove unnecessary files
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
6baa59376c refactor(kernel): normalizer
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:56 -07:00
Leonardo de Moura
eb046c11fb refactor(kernel): the type in let-exprs is not optional anymore, if the user does not provide it, we use a metavariable
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
410d5cc8ed fix(kernel): remove unnecessary file
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
16aa1ebbac refactor(kernel): replace_visitor
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
101888e079 refactor(kernel): delete update_expr
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
b5f0f28009 refactor(kernel): environment, kernel object and exceptions
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
737fe6830f test(tests/kernel): adjust expr tests
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
f986963a95 refactor(kernel): serializer and deserializer
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
74f74d2f79 refactor(kernel): shallow copy procedure
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
5da501d538 fix(kernel): style warnings
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
73c8bf4436 refactor(tests/kernel): move tests to new kernel
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
565dbe1700 fix(kernel/instantiate): bug in new head_beta_reduce
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
d17990ed78 refactor(kernel): add formatter and simplify contexts
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
53ee205dc6 fix(kernel): memory corruption bugs
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
72e1678ad9 refactor(kernel): cleanup instantiate and abstract procedures, implement update procedures
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
db31cc37a1 refactor(kernel/free_vars): cleanup free_vars procedures
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
533f44e224 refactor(kernel/expr): for_each_fn, replace_fn, and find_fn without templates
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:55 -07:00
Leonardo de Moura
69b9f2dd37 refactor(kernel/expr): for_each and find functional objects
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:54 -07:00
Leonardo de Moura
23988f528c refactor(kernel/expr): add expr constructors, and expression equality test
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:54 -07:00
Leonardo de Moura
9d3db8de1f fix(kernel/diff_cnstrs): missing include
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:54 -07:00
Leonardo de Moura
02413d7c44 refactor(kernel/expr): adding suport for universe polymorphism, and simplify metavariable representation
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:54 -07:00
Leonardo de Moura
13cfd60622 fix(kernel/diff_cnstrs): copyright msg
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:54 -07:00
Leonardo de Moura
76b1ddb967 feat(kernel): add difference constraint solver with backtracking support, and justification generation, this solver will be used to check the satisfiability of universe level constraints
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:54 -07:00
Leonardo de Moura
9f93b5d97e feat(kernel/level): new universe level datastructure for universe level polymorphism
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:54 -07:00
Leonardo de Moura
1b6b33b3f5 refactor(kernel): start version 0.2, new kernel with universe polymorphism and better/cleaner support for metavariables
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-03-18 10:27:54 -07:00
Leonardo de Moura
e9dada5e14 refactor(builtin/kernel): use standard definition for 'or' and 'and'
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-17 12:05:34 -08:00
Leonardo de Moura
c526e5ec00 feat(builtin/kernel): prove false_elim without using case
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-15 14:26:13 -08:00
Leonardo de Moura
1739b5c153 fix(kernel/type_checker): caching bug
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-12 10:43:01 -08:00
Leonardo de Moura
368fcb5ff9 refactor(builtin/kernel): rename refute to by_contradiction
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-12 08:49:19 -08:00
Leonardo de Moura
a2d2e36f04 refactor(frontends/lean): remove notation for creating tuples
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-10 09:03:42 -08:00
Leonardo de Moura
c45c1748d8 refactor(builtin/kernel): reorder congr1 arguments
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-09 16:15:44 -08:00
Leonardo de Moura
8df7c7b02d feat(kernel/type_checker): remove fallback that expands opaque definitions in the type checker
We should not rely on this feature. It can be quite expensive.
We invoke is_convertible in several places, in particular, if we are using overloading. For example, the frontend uses is_convertible to check which overload should be used. Thus, it will make several calls such as

   is_convertible(num, Nat)

If is_convertible starts unfolding opaque definitions, we would keep expanding num.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-09 11:31:24 -08:00
Leonardo de Moura
f28c56b188 feat(builtin/num): add auxiliary definitions and theorems for proving the primitive recursion theorem
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-08 19:36:17 -08:00
Leonardo de Moura
24528ff685 fix(library/elaborator): fix glitches in the elaborator that were forcing us to provide parameters explicitly
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-07 18:02:08 -08:00
Leonardo de Moura
1ec01f5757 refactor(builtin): merge pair.lean with kernel.lean, and add basic theorems
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-07 16:04:44 -08:00
Leonardo de Moura
ad7b13104f feat(*): add support for heterogeneous equality in the parser, elaborator and simplifier, adjusts unit test to reflect changes
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-07 15:03:16 -08:00
Leonardo de Moura
6d7ec9d7b6 refactor(kernel): add heterogeneous equality back to expr
The main motivation is that we will be able to move equalities between universes.

For example, suppose we have
    A : (Type i)
    B : (Type i)
    H : @eq (Type j) A B
where j > i

We didn't find any trick for deducing (@eq (Type i) A B) from H.
Before this commit, heterogeneous equality as a constant with type

   heq : {A B : (Type U)} : A -> B -> Bool

So, from H, we would only be able to deduce

   (@heq (Type j) (Type j) A B)

Not being able to move the equality back to a smaller universe is
problematic in several cases. I list some instances in the end of the commit message.

With this commit, Heterogeneous equality is a special kind of expression.
It is not a constant anymore. From H, we can deduce

   H1 : A == B

That is, we are essentially "erasing" the universes when we move to heterogeneous equality.
Now, since A and B have (Type i), we can deduce (@eq (Type i) A B) from H1. The proof term is

  (to_eq (Type i) A B (to_heq (Type j) A B H))  :  (@eq (Type i) A B)

So, it remains to explain why we need this feature.

For example, suppose we want to state the Pi extensionality axiom.

axiom hpiext {A A' : (Type U)} {B : A → (Type U)} {B' : A' → (Type U)} :
      A = A' → (∀ x x', x == x' → B x == B' x') → (∀ x, B x) == (∀ x, B' x)

This axiom produces an "inflated" equality at (Type U) when we treat heterogeneous
equality as a constant. The conclusion

     (∀ x, B x) == (∀ x, B' x)

is syntax sugar for

   (@heq (Type U) (Type U) (∀ x : A, B x) (∀ x : A', B' x))

Even if A, A', B, B' live in a much smaller universe.

As I described above, it doesn't seem to be a way to move this equality back to a smaller universe.

So, if we wanted to keep the heterogeneous equality as a constant, it seems we would
have to support axiom schemas. That is, hpiext would be parametrized by the universes where
A, A', B and B'. Another possibility would be to have universe polymorphism like Agda.
None of the solutions seem attractive.

So, we decided to have heterogeneous equality as a special kind of expression.
And use the trick above to move equalities back to the right universe.

BTW, the parser is not creating the new heterogeneous equalities yet.
Moreover, kernel.lean still contains a constant name heq2 that is the heterogeneous
equality as a constant.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-07 10:28:10 -08:00
Leonardo de Moura
30570c843f feat(builtin): add optional type
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-05 17:33:06 -08:00
Leonardo de Moura
0283887ee9 refactor(builtin/kernel): move the heq axioms into kernel.lean
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-04 14:17:34 -08:00
Leonardo de Moura
9dc86e3cf5 fix(builtin/kernel): rename generalized proof_irrel axiom to hproof_irrel, and derive the restricted one
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-04 10:06:29 -08:00
Leonardo de Moura
9a677331da feat(builtin): simulate subtypes using sigma types
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-04 01:46:50 -08:00
Leonardo de Moura
4fcc292332 feat(frontends/lean): parse and pretty print pair/tuple projection operators proj1 and proj2, fix bug in the type checker
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-03 22:10:01 -08:00
Leonardo de Moura
5c991f8fbf feat(frontends/lean): parse and pretty print tuples/pairs
This commit also fixes a bug in the type checker when processing dependent pairs.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-03 20:10:30 -08:00
Leonardo de Moura
5e5ab1429d feat(frontends/lean): parse and pretty print sigma types
This commit also fixes some bugs in the implementation of Sigma types.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-03 18:16:00 -08:00
Leonardo de Moura
8eec289ce1 feat(kernel): add dependent pairs
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-03 16:52:49 -08:00
Leonardo de Moura
c56df132b8 refactor(kernel): remove semantic attachments from the kernel
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-02 14:48:27 -08:00
Leonardo de Moura
2aaded261e fix(kernel/environment): imported predicate
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-30 23:02:19 -08:00
Leonardo de Moura
4d533c6a25 feat(builtin/kernel): add nonempty_range theorem
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-30 22:13:34 -08:00
Leonardo de Moura
ddaf948c72 feat(builtin/kernel): add nonempty_fun theorem
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-30 19:38:51 -08:00
Leonardo de Moura
759aa61f70 refactor(builtin/kernel): define if-then-else using Hilbert's operator
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-30 19:28:42 -08:00
Leonardo de Moura
8c1f6b9055 fix(kernel/typechecker): allow elaborator to infer (Type U+1)
In the new test elab8.lean, the parameter B is in (Type U+1).
Before, this commit, the type checker was forcing all metavariables that must be types to be <= (Type U). This restriction was preventing the elaborator from succeeding in reasonable cases.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-30 14:00:01 -08:00
Leonardo de Moura
01259b1e84 feat(kernel): make sure U is the maximal universe
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-29 16:31:00 -08:00
Leonardo de Moura
24452289dd feat(library/simplifier): make sure the simplifier can handle meta-variables
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-28 20:30:47 -08:00
Leonardo de Moura
b6985bd713 feat(builtin/kernel): add another rewrite rule
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-28 15:56:26 -08:00
Leonardo de Moura
55fde28954 feat(kernel/type_checker): optionally provide metavariable environment in the methods: is_definitionally_equal, is_convertible and ensure_pi
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-27 17:47:03 -08:00
Leonardo de Moura
160dc71cb5 refactor(kernel/type_checker): use read-only metavariable environment in methods that do not require write access to the metavariable environment
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-27 17:38:06 -08:00
Leonardo de Moura
05b4d8411b refactor(kernel/normalizer): normalizer only needs read access to metavariable environment
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-27 17:03:36 -08:00
Leonardo de Moura
3b152d1a9e refactor(kernel): use ro_metavar_env instead of metavar_env in places where we only need to read the metavariable environment
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-27 16:44:43 -08:00
Leonardo de Moura
b26035fcf6 feat(kernel/type_checker): improve application type mismatch error messages
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-27 09:45:17 -08:00
Leonardo de Moura
ceff335bb8 doc(doc/lean/tutorial): update tutorial
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-26 22:58:44 -08:00
Leonardo de Moura
4d25cb7f47 feat(library/tactic): add simplify_tactic based on the simplifier
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-26 18:53:18 -08:00
Leonardo de Moura
9fb3ccb4c0 feat(library/simplifier): support for dependent simplification in lambda expressions
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-25 16:54:42 -08:00
Leonardo de Moura
2bb33c55fe feat(builtin/kernel): add more theorems useful for simplification
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-24 18:52:50 -08:00
Leonardo de Moura
26bea77721 fix(library/simplifier): bug in heterogeneous equality support, and universe commutativity support in the simplifier
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-24 17:09:46 -08:00
Leonardo de Moura
dbc100cc2e feat(library/simplifier): cast elimination in the simplifier
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-23 17:28:14 -08:00