Oak is a proof checker focused on simplicity, readability, and ease of use.

For downloads and more information, including a tutorial, go to oakproof.org.

• Ruby programming language version ≥ 2.0
• E theorem prover version 2.3. E is included in the prepackaged Oak downloads available at oakproof.org. If you prefer to install E yourself, be sure to add E's PROVER directory to your system's PATH variable so that Oak will detect it.

• The Atom text editor has a package language-oak which provides syntax highlighting, automatic indentation, and comment toggling for Oak.

Oak is a command-line application which takes a proof file as input, and tells you whether or not the proof is correct. See oakproof.org for more information.

oak [-v] [-c] [-w] [filename]
  -v  print the version number of Oak
  -c  check for unneeded citations
  -w  wait for validity if unknown (does not change proof outcome)

• new examples: infinite_primes.oak and set.oak
• merged peano.oak into naturals.oak and expanded
• -w option to wait for validity if unknown
• extra check to ensure A implies A always succeeds
• added not in condition
• added for at most one quantifier
• improved assumption printing
• simplified quantifier variable list syntax
• exit now skips rest of proof, not just current file
• proofs with exit are now marked incomplete

• add "tie-ins" for variables
• -c option to check for unneeded citations
• new examples: kalam.oak and square_root_two.oak
• print notice when exit is called

• performance improvement from internal reworking of scopes/bindings
• variables bound with define can no longer be re-bound in the same scope

• initial release

Many thanks to Stephan Schulz, the author of E, for answering questions and adding options to E to better support Oak.