README for beautifHOL, a HOL prettyprinter

Based on the paper found at http://www.cs.indiana.edu/~lepike/pub_pages/pphol.html

Lee Pike <lee-pike-@-gma-il-.com> (remove dashes)

Jan 5, 2009

Copyright 2008

This file is part of beautifHOL.

BSD3.

This README contains the following sections:

• Program Description
• License information
• Installation information
• Usage information
• How to modify the program
• Todos (including known bugs)

==DESCRIPTION==

This is a pretty-printer for higher-order logic (HOL). It reads in a formula and outputs it to standard out. More information about the pretty-printer can be found in the paper, "How to Pretty-Print a Long Formula" http://www.cs.indiana.edu/~lepike/pubs/pike-holpp.pdf.

==LICENSE==

BSD3 license.

==INSTALLATION==

This program is distributed as a Cabal package, a packaging system for Haskell programs. For information on how to install a Cabal package, see http://www.haskell.org/haskellwiki/Cabal/How_to_install_a_Cabal_package. The easiest way to install a Cabal package is to use cabal-install: http://hackage.haskell.org/trac/hackage/wiki/CabalInstall. Instructions for getting cabal-install are located there.

==USAGE==

If you install this program using Cabal (describe above), then the executable, beautifulHOL, should be in your path. Then issue

      > beautifHOL

to interact with the program in a read-eval-print loop. From there, you can enter HOL formulas. Examples of the syntax can be found in the file formulas.txt. Be sure to terminate a formula with a semicolon. After entering a formula, its pretty-printed rendering will be sent to standard out.

The available options to the program can be seen by issuing

      > beautifHOL --help

Among others, there is an option to suppress labels (--nolabel) and an option to read in a set of formulas from a file and print their renderings to standard-out. For example, issuing

      > beautifHOL --f formulas.txt

will render all the example formulas.

==MODIFYING THE PROGRAM==

== MODIFYING THE INPUT LANGUAGE

The syntax of the current input language is documented in http://www.cs.indiana.edu/~lepike/pub_pages/docHOL.pdf.

To modify the input language to use with other variants of HOL, you will need the BNF Converter (BNFC). BNFC is an GPL-licensed that generates a compiler-front end from a labeled Bakus Normal Form language specification. It also generates docs, etc. BNFC is available at http://www.cs.chalmers.se/Cs/Research/Language-technology/BNFC/. The latest version can be obtained by issuing

darcs get --partial http://www.cs.chalmers.se/Cs/Research/Language-technology/darcs/BNFC/

BNFC will generate new files for you based on your new input language. The current input language is defined in HOL.cf as a labeled BNF grammar. Edit this file. BE SURE to move or rename PrintHOL.hs, ConfigHOL.hs, and TestHOL.hs when generating new files as BNFC will overwrite these files (which have been modified in beautifHOL). After generation from BNFC, overwrite the generated files and compile as usual. If you have added new language constructs, you will have to add corresponding cases to PrintHOL.hs.

== MODIFYING ANYTHING ELSE

If you want to modify only the output syntax or the pretty-printing style, you need only to modify one or more of the following files:

• PrintHOL.hs, the guts of the pretty-printer.
• ConfigHOL.hs, where user-defined constants are (e.g., the output syntax for conjunction, the maximum length of a formula on a line, etc.).
• TestHOL.hs, where main is defined.

You do NOT need BNFC to make these modifications. Simply rebuild the program by issuing

ghc --make TestHOL.hs -o beautifHOL or runhaskell Setup.lhs configure runhaskell Setup.lhs build runhaskell Setup.lhs install

BE SURE TO SEND ME ANY PATCHES!

==TODOs==

==Code Cleanups==

• Remove dead code.
• Run HPC and HLint over this.
• How spaces are handled needs to be reimplemented.
• Should be reimplemented to use SPJ/John Hughes pretty-printing library: pretty on Hackage http://hackage.haskell.org/cgi-bin/hackage-scripts/package/pretty.

==New Functionality==

• Desired new functionality is described in the accompanying paper, "How to Pretty-Print a Long Formula" (pphol.pdf).
• Better parse-error messages.

==Bugs/Issues==

• Can't have a breakline char -- it'll break things if it's really a string (e.g., Latex).
• There are known issues with using different widths for spcStr, argSepStr, etc.
• Parsing doesn't work if there is whitespace between relation or function identifiers and parentheses.
• In ConfigHOL.hs, "in" is defined "in " to fix a pretty-printing bug.