Pantograph

An interaction system for Lean 4.

Installation

Install elan and lean4. Then, execute

lake build

In order to use mathlib, its binary must also be built

lake build Qq
lake build aesop
lake build std
lake build mathlib

Usage

The binary must be run inside a lake env environment. i.e. lake env build/bin/pantograph OPTIONS|MODULES. The REPL loop accepts commands as single-line JSON inputs and outputs either an Error: (indicating malformed command) or a json return value indicating the result of a command execution. The command can be passed in one of two formats

command { ... }
{ "cmd": command, "payload": ... }

The list of available commands can be found in Pantograph/Commands.lean. An empty command aborts the REPL.

The Pantograph executable must be run with a list of modules to import. It can also accept options of the form --key=value e.g. --pp.raw=true.

Example: (~5k symbols)

$ lake env build/bin/Pantograph "Init"
catalog
inspect {"name": "Nat.le_add_left"}

Example with mathlib (~90k symbols)

$ lake env build/bin/Pantograph "Mathlib.Analysis.Seminorm"
catalog

Example proving a theorem: (alternatively use proof.start {"copyFrom": "Nat.add_comm"}) to prime the proof

$ lake env build/bin/Pantograph "Init"
proof.start {"expr": "∀ (n m : Nat), n + m = m + n"}
proof.tactic {"treeId": 0, "stateId": 0, "goalId": 0, "tactic": "intro n m"}
proof.tactic {"treeId": 0, "stateId": 1, "goalId": 0, "tactic": "assumption"}
proof.printTree {"treeId": 0}
proof.tactic {"treeId": 0, "stateId": 1, "goalId": 0, "tactic": "rw [Nat.add_comm]"}
proof.printTree {"treeId": 0}

where the application of assumption should lead to a failure.

Troubleshooting

If lean encounters stack overflow problems when printing catalog, execute this before running lean:

ulimit -s unlimited

Testing

The tests are based on LSpec. To run tests,

test/all.sh