Commit graph

226 commits

Author SHA1 Message Date
Leonardo de Moura
fbf13994d8 refactor(*): use + for concatenating format objects
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-08-24 09:35:25 -07:00
Leonardo de Moura
d4ac482d76 refactor(kernel): move annotation to library
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-08-22 10:38:10 -07:00
Leonardo de Moura
f5987b7bda refactor(library/unifier): make it easier to add new options to the unifier
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-08-20 17:30:08 -07:00
Leonardo de Moura
9588336c15 refactor(kernel/type_checker): remove "global" constraint buffer from type_checker, and use constraint_seq instead
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-08-20 16:46:19 -07:00
Leonardo de Moura
4cf3d32e0c chore(*): create alias for std::pair
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-08-20 16:46:19 -07:00
Leonardo de Moura
2869d9059f feat(frontends/lean): change 'proof-qed' semantics: no backtracking
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-08-12 17:40:30 -07:00
Leonardo de Moura
562926e7ad refactor(kernel/instantiate): add functions instantiate_value_univ_params and instantiate_type_univ_params
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-08-12 17:40:30 -07:00
Leonardo de Moura
f896771987 refactor(library/tactic/expr_to_tactic): use annotations for implementing 'by'
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-08-10 11:16:46 -07:00
Leonardo de Moura
8bd36dabce refactor(kernel/pos_info_provider): get_pos_info return none if position is not available
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-08-01 20:17:26 -07:00
Leonardo de Moura
faee08591f fix(*): make sure elaborator and type_checker use the same "rules" for treating opaque definitions
This is a big change because we have to store in constraints whether we can use the "relaxed" rules or not.
The "relaxed" case says that when type checking the value of an opaque definition we can treat other opaque definitions in the same module as transparent.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-27 12:12:54 -07:00
Leonardo de Moura
13fe28dd1c perf(library/unifier): delay the instantiation of metavariables occurring in the types of local constants
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-23 14:31:30 -07:00
Leonardo de Moura
61661478ad refactor(kernel/metavar): simplify substitution class, and remove dead code
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-23 10:03:03 -07:00
Leonardo de Moura
d69db172a1 chore(kernel/replace_fn): add syntax sugar for replace function
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-19 12:53:37 +01:00
Leonardo de Moura
b62abf0f06 refactor(library/tactic/goal): remove redundance, goal pp method was duplicating some of the functionality provided by the pretty printer
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-10 18:59:03 +01:00
Leonardo de Moura
405e57eb2d refactor(kernel/formatter): add formatter_factory, and simplify formatter interface
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-10 18:32:00 +01:00
Leonardo de Moura
91b0dcad0f fix(library/tactic): avoid 'unknown' message in trace_tac when position information is not available
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-08 17:48:41 -07:00
Leonardo de Moura
a1601e7a5f feat(library/tactic/apply_tactic): add option for 'refreshing' universe metavariables in the 'apply' tactic
The new test ../../tests/lean/run/tactic27.lean demonstrates why we need this feature. The tactic 'apply @refl' is actually 'apply @refl.{?l}'. It is used inside of a repeat tactical. Each iteration of the 'repeat' may need to use a different value for ?l. Before this commit, there was not way to say we want a fresh ?l each iteration.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-08 16:55:23 -07:00
Leonardo de Moura
a3be63af73 feat(frontends/lean): add tactic_hint command
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-08 15:08:13 -07:00
Leonardo de Moura
ab929d7201 refactor(library/unifier): store the unifier_plugin in the environment
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-05 10:25:58 -07:00
Leonardo de Moura
e0501104e2 feat(library/tactic): add 'fixpoint' tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-04 01:30:28 -07:00
Leonardo de Moura
abbd054b51 feat(library/tactic): add eassumption tactic, and remove redundant 'subgoals' from apply tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-03 13:04:46 -07:00
Leonardo de Moura
dd96bb151b refactor(library/unifier): reduce the number unify procedure 'flavors'
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-03 11:15:43 -07:00
Leonardo de Moura
0ff145e59b feat(library/tactic): add apply tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-03 09:20:01 -07:00
Leonardo de Moura
e3ab0a1d10 feat(frontends/lean): improve error messages when users forget to import 'tactic'
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-03 08:33:29 -07:00
Leonardo de Moura
6b8b5f3dd8 feat(library/tactic): expose more builtin tactics, cleanup expr_to_tactic procedure
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-03 08:06:28 -07:00
Leonardo de Moura
a7d660f875 feat(frontends/lean): add command for customizing the behavior of proof-qed blocks: we can automatically register tactics to be automatically applied before each component
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 20:45:10 -07:00
Leonardo de Moura
5527955ba8 feat(frontends/lean): add 'proof-qed' notation
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 19:30:48 -07:00
Leonardo de Moura
138267b53a feat(frontends/lean/elaborator) add trick for improving error messages when mixing tactics, elaboration and exact tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 18:58:32 -07:00
Leonardo de Moura
60c637fb9d feat(library/tactic): add 'exact' tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 18:37:32 -07:00
Leonardo de Moura
37b5b7c4c2 feat(library/tactic): rename 'exact' to 'assumption', 'exact' is a different tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 18:10:42 -07:00
Leonardo de Moura
6a6ebd5c2d refactor(kernel/metavar): add method instantiate as alias for instantiate_metavars_wo_jst
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 15:39:25 -07:00
Leonardo de Moura
3e1bb96935 feat(library/tactic/goal): propagate tag (for position information) from goal to subgoal
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 14:47:18 -07:00
Leonardo de Moura
ee531ec0e2 feat(frontends/parser): improve error message when an apply tactic refers a local constant that is not marked as [fact]
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 14:09:01 -07:00
Leonardo de Moura
0f27856e4a feat(library/tactic): new apply tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 13:14:50 -07:00
Leonardo de Moura
6ab46396d8 feat(library/tactic): expose 'trace' tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 10:52:45 -07:00
Leonardo de Moura
e1d909455c refactor(library/tactic): add namespace 'tactic', improve expr_to_tactic failure error message
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 10:45:09 -07:00
Leonardo de Moura
7593ee1468 refactor(library/standard): remove parameter from 'tactic' inductive type
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-02 08:09:24 -07:00
Leonardo de Moura
b2b76b078f feat(frontends/lean): remove build_tactic_cmds, and use expressions for representing tactics
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-01 20:43:53 -07:00
Leonardo de Moura
cbac21ec7f feat(library/tactic): add trick for 'embedding' tactics inside Lean expressions
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-01 19:05:22 -07:00
Leonardo de Moura
2df92b0701 refactor(library/tactic): simplify proof_state
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-01 18:02:17 -07:00
Leonardo de Moura
4cb5f97038 refactor(library/tactic): simplify tactic framework, no more proof builders
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-07-01 16:11:19 -07:00
Leonardo de Moura
cb000eda13 refactor(kernel): store binder_infor in local constants
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-30 11:37:46 -07:00
Leonardo de Moura
c2ab31113f refactor(library/tactic): remove cex_builder and 'precision' for proof_state's
These two features make sense for solvers, but not in a general purpose tactic framework for building proofs like the one in Lean.

In most cases, we cannot build a counterexample anyway. These two features should be added in a custom framework for combining preprocessing techniques like in Z3.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-30 08:48:07 -07:00
Leonardo de Moura
8d584e54da feat(frontends/lean): add exact_apply
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-30 00:51:11 -07:00
Leonardo de Moura
360e9b9486 feat(library/tactic): add apply tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-29 18:33:53 -07:00
Leonardo de Moura
a8f9594046 refactor(kernel/instantiate): rename instantiate_params to instantiate_univ_params
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-29 12:09:55 -07:00
Leonardo de Moura
937d7b2813 fix(library/tactic): unfold tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-29 12:04:58 -07:00
Leonardo de Moura
6d09d82a7c feat(frontends/lean): add notation for orelse tactic, add show and now tactics
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-29 11:39:18 -07:00
Leonardo de Moura
a1bbb09de4 feat(frontends/lean): add notation for then tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-29 11:24:56 -07:00
Leonardo de Moura
15f270d9f3 fix(library/tactic): memory leak that only happens when compiling with clang++
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-29 11:07:06 -07:00
Leonardo de Moura
e408998e06 fix(library/tactic): name convention
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-27 18:42:59 -07:00
Leonardo de Moura
fa72e7b874 refactor(library/tactic): simplify tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-27 18:35:59 -07:00
Leonardo de Moura
5524c6c3d8 refactor(library/tactic/proof_state): simplify proof state
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-27 14:49:48 -07:00
Leonardo de Moura
c6ac89d967 refactor(library/tactic/proof_builder): simplify proof builder
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-27 12:25:04 -07:00
Leonardo de Moura
aaa7960b75 refactor(library/tactic/goal): use local names for hypotheses
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-27 11:11:12 -07:00
Leonardo de Moura
d84b745241 refactor(library/tactic/cex_builder): simplify cex_builder
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-27 07:14:33 -07:00
Leonardo de Moura
b4e4c4d610 chore(library/tactic): remove unnecessary file
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-27 07:02:13 -07:00
Leonardo de Moura
f1d8d8dcf9 chore(library/tactic): update goal objects
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-27 07:00:12 -07:00
Leonardo de Moura
ad70044ae1 chore(library/tactic): remove dead code
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-27 07:00:12 -07:00
Leonardo de Moura
77c5319c4a chore(*): remove Lua 'migrate'
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-06-18 07:01:34 -07:00
Leonardo de Moura
2d70e2f4f2 fix(library/tactic/goal): bug in the proof builder
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-09 15:02:36 -08:00
Leonardo de Moura
1c43020fc9 fix(library/tactic/goal): bug creating main proof builder
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-08 09:11:07 -08:00
Leonardo de Moura
f4ec874c6e refactor(builtin): remove dead module heq
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-04 14:42:28 -08:00
Leonardo de Moura
110ca84984 feat(library/simplifier): allow the user to associate a simplifier monitor with the lua_State object
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-31 13:49:24 -08:00
Leonardo de Moura
41f5e2a067 feat(library/simplifier): statically check (conditional) equations (aka rewrite rules) to verify whether we can skip type checking when using them in the simplifier
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-29 18:32:40 -08:00
Leonardo de Moura
069e5edf6b fix(library/simplifier): include flag indicating if the proof generated by simplifier is a homogenous or heterogenous equality, use flag to fix bug in the simp_tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-29 12:01:01 -08:00
Leonardo de Moura
92ba4e8b2d feat(library/simplifier): add support for metavariables in conditional rewrite rules
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-29 08:34:04 -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
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
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
14c6218bdc chore(kernel): file name convention
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-15 20:06:29 -08:00
Leonardo de Moura
411f14415d feat(builtin): automatically generate Lean/C++ interface for builtin theories
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-09 18:09:53 -08:00
Leonardo de Moura
abf61be8f6 chore(library/tactic): remove imp_tac, it is not needed anymore
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-08 00:57:04 -08:00
Leonardo de Moura
0592261847 refactor(kernel/io_state): move io_state_stream to library
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-01-02 13:14:21 -08:00
Leonardo de Moura
ecd62a1783 refactor(builtin/basic): rename basic.lean to kernel.lean
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-30 11:46:03 -08:00
Leonardo de Moura
72761f14e4 refactor(library/io_state): move to the kernel
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-30 11:20:23 -08:00
Leonardo de Moura
df3686634d refactor(kernel/builtin): remove unnecessary predicates
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-29 12:20:29 -08:00
Leonardo de Moura
411ebbc3c1 refactor(library/basic_thms): move the proof of all basic theorems to a .Lean file
This commit also adds several new theorems that are useful for implementing the simplifier.
TODO: perhaps we should remove the declarations at basic_thms.h?

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-29 03:04:49 -08:00
Leonardo de Moura
f1b97b18b4 refactor(frontends/lean/parser): tactic macros, and tactic Lua bindings
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-26 15:54:53 -08:00
Leonardo de Moura
88235d2922 feat(library/tactic/apply_tactic): try other solutions produced by the elaborator
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-25 11:51:27 -08:00
Leonardo de Moura
8e45064f25 feat(library/tactic/apply_tactic): improved parametric apply_tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-24 22:40:34 -08:00
Leonardo de Moura
75cf751959 feat(library/tactic/apply_tactic): allow apply_tac Lua binding to take expressions as argument
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-24 16:03:16 -08:00
Leonardo de Moura
6cc57cc4b5 fix(library/tactic/apply_tactic): bug in apply_tac
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-24 15:54:56 -08:00
Leonardo de Moura
cb95b14332 feat(library/tactic/apply_tactic): improve apply_tactic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-24 14:23:06 -08:00
Soonho Kong
de018220e1 feat(*): use std::make_shared to create shared_ptr 2013-12-24 14:32:50 -05:00
Leonardo de Moura
3e32d9bef2 feat(library/tactic): add support for Pi's at to_proof_state
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-22 16:40:55 -08:00
Leonardo de Moura
104bd990e1 feat(library/tactic): add normalize_tac, eval_tac and trivial_tac
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-22 14:10:42 -08:00
Leonardo de Moura
4229e498d2 refactor(kernel/type_checker): combine type_checker and type_inferer into a single class, and avoid code duplication
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-22 11:51:38 -08:00
Leonardo de Moura
4d05a8b65b fix(library/tactic/apply_tactic): provide the metavar_env to instantiate, the goal is to avoid add_lift and add_inst local entries
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-20 14:17:04 -08:00
Leonardo de Moura
7772c16033 refactor(kernel): add unfold_opaque flag to normalizer, modify how type checker uses the opaque flag, remove hidden_defs, and mark most builtin definitions as opaque
After this commit, in the type checker, when checking convertability, we first compute a normal form without expanding opaque terms.
If the terms are convertible, then we are done, and saved a lot of time by not expanding unnecessary definitions.
If they are not, instead of throwing an error, we try again expanding the opaque terms.
This seems to be the best of both worlds.
The opaque flag is a hint for the type checker, but it would never prevent us from type checking  a valid term.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-20 12:47:47 -08:00
Leonardo de Moura
10f28c7bec feat(kernel/replace_fn): non-recursive replace_fn
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-17 16:35:39 -08:00
Leonardo de Moura
51aee83b70 refactor(kernel/metavar_env): use the same approach used in the class environment in the class metavar_env
This modification was motivated by a bug exposed by tst17 at tests/kernel/type_checker.
metavar_env is now a smart point to metavar_env_cell.
ro_metavar_env is a read-only smart pointer. It is useful to make sure we are using proof_state correctly.

example showing that the approach for caching metavar_env is broken in the type_checker

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-13 18:59:15 -08:00
Leonardo de Moura
2e5e5e187f chore(util/rc): remove unnecessary argument from LEAN_COPY_REF and LEAN_MOVE_REF macros
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-13 15:01:24 -08:00
Leonardo de Moura
450d6a4b1e refactor(util/splay_tree): replace find with splay_find
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-12 17:27:30 -08:00
Leonardo de Moura
f97c260b0b refactor(kernel/environment): add ro_environment
The environment object is a "smart-pointer".
Before this commit, the use of "const &" for environment objects was broken.
For example, suppose we have a function f that should not modify the input environment.
Before this commit, its signature would be
       void f(environment const & env)
This is broken, f's implementation can easilty convert it to a read-write pointer by using
the copy constructor.
       environment rw_env(env);
Now, f can use rw_env to update env.

To fix this issue, we now have ro_environment. It is a shared *const* pointer.
We can convert an environment into a ro_environment, but not the other way around.

ro_environment can also be seen as a form of documentation.
For example, now it is clear that type_inferer is not updating the environment, since its constructor takes a ro_environment.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-12 16:48:34 -08:00
Leonardo de Moura
3457fe5935 chore(kernel): rename read_only_environment and read_write_environment
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-12 16:48:33 -08:00
Leonardo de Moura
c0b9c7ffc4 refactor(library/io_state): simplify regular/diagnostic
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-10 13:09:35 -08:00
Leonardo de Moura
8f2fe273ea refactor(*): isolate std::thread dependency
This commit allows us to build Lean without the pthread dependency.
It is also useful if we want to implement multi-threading on top of Boost.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-09 15:20:26 -08:00
Leonardo de Moura
8add5571f1 refactor(library/tactic): remove 'null' tactic, and operator bool tactics
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-08 15:00:16 -08:00
Leonardo de Moura
04b67f8b14 refactor(kernel/object): remove 'null' object, and operator bool for kernel objects
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-08 14:37:38 -08:00