Cosh

Cosh is an experimental Church implementation that uses dynamic programming based on hashing factored continuations.

Installation

This installation assumes that you have git and a R6RS Scheme installed. The instructions on the Church wiki describe how to install Vicare Scheme with foreign function interface enabled.

1. Install scheme-tools:

   1. Clone the scheme-tools repository using git clone git://github.com/stuhlmueller/scheme-tools.git.

   2. Add the scheme-tools directory to your $VICARE_LIBRARY_PATH.

      To add a directory to your $VICARE_LIBRARY_PATH, change into the directory and type echo -e "\nexport VICARE_LIBRARY_PATH=`pwd`:$VICARE_LIBRARY_PATH" >> /.bashrc. Replace /.bashrc with the location of your shell config file.

   3. Add the scheme-tools/bin directory to your $PATH.

      To add a directory to your $PATH, cd into the directory and type echo -e "\nexport PATH=`pwd`:$PATH" >> ~/.bashrc.

2. Install scheme-transforms:

   1. Clone the repository using git clone git://github.com/stuhlmueller/scheme-transforms.git.

   2. Add the scheme-transforms directory to your $VICARE_LIBRARY_PATH (see above).

3. Install cosh:

   1. Clone the repository using git clone git://github.com/stuhlmueller/cosh.git.

   2. Add the cosh directory to your $VICARE_LIBRARY_PATH (see above).

   3. Add the cosh/bin directory to your $PATH (see above).

4. Reload your shell config file, e.g., via source ~/.bashrc.

Usage

Create a file called myprogram.church with the following content:

(rejection-query
 (define x (flip))
 (define y (flip))
 (list x y)
 (or x y))

Then, on the command line, type:

cosh myprogram.church

You should see the following output:

(#f #t): 0.3333333333333332 (-1.09861228866811)
(#t #f): 0.3333333333333332 (-1.09861228866811)
(#t #t): 0.3333333333333332 (-1.09861228866811)

This shows the probability (and log probability) of each possible program return value.

Options

$ cosh --help
Usage: cosh <file> [options]

Options:
  -h, --help            show this help message and exit
  -d, --debug           run all scheme commands in debug mode
  -k, --keep            do not delete compiled file
  -l LIMIT, --limit=LIMIT
                        restrict graph size
  -v, --verbose         display all executed commands
  -t, --time            record runtime