140 lines
4.9 KiB
Markdown
140 lines
4.9 KiB
Markdown
# Pantograph
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A Machine-to-Machine interaction system for Lean 4.
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Pantograph provides interfaces to execute proofs, construct expressions, and
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examine the symbol list of a Lean project for machine learning.
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## Installation
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For Nix based workflow, see below.
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Install `elan` and `lake`. Execute
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``` sh
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make build/bin/pantograph
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```
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setup the `LEAN_PATH` environment variable so it contains the library path of lean libraries. The libraries must be built in advance. For example, if `mathlib4` is stored at `../lib/mathlib4`,
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``` sh
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LIB="../lib"
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LIB_MATHLIB="$LIB/mathlib4/lake-packages"
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export LEAN_PATH="$LIB/mathlib4/build/lib:$LIB_MATHLIB/aesop/build/lib:$LIB_MATHLIB/Qq/build/lib:$LIB_MATHLIB/std/build/lib"
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LEAN_PATH=$LEAN_PATH build/bin/pantograph $@
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```
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The provided `flake.nix` has a develop environment with Lean already setup.
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## Executable Usage
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``` sh
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pantograph MODULES|LEAN_OPTIONS
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```
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The REPL loop accepts commands as single-line JSON inputs and outputs either an
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`Error:` (indicating malformed command) or a JSON return value indicating the
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result of a command execution. The command can be passed in one of two formats
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```
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command { ... }
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{ "cmd": command, "payload": ... }
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```
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The list of available commands can be found in `Pantograph/Protocol.lean` and below. An
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empty command aborts the REPL.
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The `pantograph` executable must be run with a list of modules to import. It can
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also accept lean options of the form `--key=value` e.g. `--pp.raw=true`.
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Example: (~5k symbols)
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```
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$ pantograph Init
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env.catalog
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env.inspect {"name": "Nat.le_add_left"}
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```
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Example with `mathlib4` (~90k symbols, may stack overflow, see troubleshooting)
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```
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$ pantograph Mathlib.Analysis.Seminorm
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env.catalog
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```
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Example proving a theorem: (alternatively use `goal.start {"copyFrom": "Nat.add_comm"}`) to prime the proof
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```
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$ pantograph Init
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goal.start {"expr": "∀ (n m : Nat), n + m = m + n"}
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goal.tactic {"stateId": 0, "goalId": 0, "tactic": "intro n m"}
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goal.tactic {"stateId": 1, "goalId": 0, "tactic": "assumption"}
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goal.delete {"stateIds": [0]}
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stat {}
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goal.tactic {"stateId": 1, "goalId": 0, "tactic": "rw [Nat.add_comm]"}
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stat
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```
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where the application of `assumption` should lead to a failure.
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### Commands
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See `Pantograph/Protocol.lean` for a description of the parameters and return values in JSON.
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- `reset`: Delete all cached expressions and proof trees
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- `expr.echo {"expr": <expr>}`: Determine the type of an expression and round-trip it
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- `env.catalog`: Display a list of all safe Lean symbols in the current environment
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- `env.inspect {"name": <name>, "value": <bool>}`: Show the type and package of a
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given symbol; If value flag is set, the value is printed or hidden. By default
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only the values of definitions are printed.
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- `options.set { key: value, ... }`: Set one or more options (not Lean options; those
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have to be set via command line arguments.), for options, see `Pantograph/Protocol.lean`
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- `options.print`: Display the current set of options
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- `goal.start {["name": <name>], ["expr": <expr>], ["copyFrom": <symbol>]}`: Start a new goal from a given expression or symbol
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- `goal.tactic {"stateId": <id>, "goalId": <id>, ["tactic": <tactic>], ["expr": <expr>]}`: Execute a tactic string on a given goal
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- `goal.continue {"stateId": <id>, ["branch": <id>], ["goals": <names>]}`: Continue from a proof state
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- `goal.remove {"stateIds": [<id>]}"`: Remove a bunch of stored goals.
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- `goal.print {"stateId": <id>}"`: Print a goal state
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- `stat`: Display resource usage
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### Errors
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When an error pertaining to the execution of a command happens, the returning JSON structure is
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``` json
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{ error: "type", desc: "description" }
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```
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Common error forms:
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* `command`: Indicates malformed command structure which results from either
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invalid command or a malformed JSON structure that cannot be fed to an
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individual command.
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* `index`: Indicates an invariant maintained by the output of one command and
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input of another is broken. For example, attempting to query a symbol not
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existing in the library or indexing into a non-existent proof state.
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### Troubleshooting
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If lean encounters stack overflow problems when printing catalog, execute this before running lean:
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```sh
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ulimit -s unlimited
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```
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## Library Usage
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`Pantograph/Library.lean` exposes a series of interfaces which allow FFI call
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with `Pantograph` which mirrors the REPL commands above. It is recommended to
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call Pantograph via this FFI since it provides a tremendous speed up.
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## Developing
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### Testing
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The tests are based on `LSpec`. To run tests,
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``` sh
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make test
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```
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## Nix based workflow
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The included Nix flake provides build targets for `sharedLib` and `executable`.
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The executable can be used as-is, but linking against the shared library
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requires the presence of `lean-all`.
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To run tests:
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``` sh
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nix build .#checks.${system}.test
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```
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For example, `${system}` could be `x86_64-linux`. Using `nix develop` drops the
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current session into a development shell with fixed Lean version.
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