README for YAP6

This directory contains a release of the YAP 6.2.* Prolog system,
originally developed at the Universidade do Porto by Luis Damas and
Vitor Santos Costa, with contributions from the Edinburgh Prolog
library, the C-Prolog manual authors, Ricardo Lopes, Ricardo Rocha,
M. Hermenegildo, D. Cabeza, Eric Alphonse, Paulo Moura, Nuno Fonseca,
Jan Wielemaker, Paul Singleton, Fred Dushin, Jan Wielemaker, Markus
Triska, and many others. You should read the rest of this file for
information on what YAP is and for instructions on how to build it.

YAP 6 has been built with several versions on GCC on a variety of
Linux, MacOSX. It has been built on Windows XP and VISTA using the
mingw toolkit and cygwin from Cygnus Solutions.

The main core of the YAP distribution is distributed under a dual
license: the Perl Artistic license 2 and the FSF's LGPL. The YAP
distribution also contains files distributed under the LGPL
exclusively, and under the GPL.

The YAP distribution includes several packages ported to YAP, such as
Pillow, JPL, CLP(R) and CHR. We would like to take the opportunity to
thank the developers of these packages for their generosity in
allowing YAP to distribute these packages. Any bugs in these packages
are probably our fault.

If you have a question about this software, desire to add code, found
a bug, want to request a feature, or wonder how to get further
assistance, please send e-mail to To
subscribe to the mailing list or access the list archives, please see

Online documentation is available for YAP at:

Recent versions of YAP, including both source and selected binaries,
can be found from this same URL.

1. What is YAP

The YAP Prolog System is a high-performance Prolog compiler developed
at LIACC, Universidade do Porto. YAP provides several important

 o speed: YAP is widely considered one of the fastest available Prolog

 o functionality: it supports stream I/O, sockets, modules,
exceptions, Prolog debugger, C-interface, dynamic code, internal
database, DCGs, saved states, co-routining, arrays.

 o we explicitly allow both commercial and non-commercial use of YAP.

YAP is based on the David H. D. Warren's WAM (Warren Abstract
Machine), with several optimizations for better performance. YAP
follows the Edinburgh tradition, and was originally designed to be
largely compatible with DEC-10 Prolog, Quintus Prolog, and especially
with C-Prolog.

YAP implements most of the ISO-Prolog standard. We are striving at
full compatibility, and the manual describes what is still
missing. The manual also includes a (largely incomplete) comparison
with SICStus Prolog.
2. Obtaining YAP's development sources.

YAP is now being maintained using the git source management system. A
public repository is available at

Please use

git clone git://

to obtain a copy of the current YAP tree.

3. How to compile YAP

First, make sure you have gmp and readline development packages
installed. If you plan to use ProbLog, also check for cudd.

Now, to compile YAP from the source directory just do:

 (1) ./configure

 (2) check the Makefile for any extensions or changes you want to make.

 (3) make

 (4) If the compilation succeeds, try ./yap

 (5) Happy? "make install"

 (6) "make install_info" will create the info files in the standard
     info directory.

 (7) "make html" will create documentation in html format in the
     current directory.

In most systems you will need to be superuser in order to do "make
install" and "make info" on the standard system directories.

3.1 Where to install YAP

 YAP uses autoconf. Recent versions of YAP try to follow GNU
conventions on where to place software. By default, this location is
/usr/local on Unix, Linux, and OS/X machines. 

You can use the --prefix configure option to set the ROOTDIR macro and
the --exec-prefix option to set the EROOTDIR macro (for
architecture-dependent files). EROOTDIR defaults to ROOTDIR.

  o The main executable is placed at BINDIR, which defaults at
$(EROOTDIR)/bin. This executable is actually a script that calls the
Prolog engine, stored at YAPLIBDIR.

  o SHAREDIR is the directory where the Prolog libraries are stored.
Its default value is $(ROOTDIR)/share. The Prolog libraries are
machine-independent text files that only need to be installed once,
even on systems where multiple copies of YAP of the same version are
installed. (e.g. with different configurations or for different
architectures sharing a file server.)

  o LIBDIR is the directory where binary libraries are stored. It is
set to $(EROOTDIR)/lib by default. YAPLIBDIR is a subdirectory (by
default $(EROOTDIR)/lib/YAP) that contains the Prolog engine and the
binary Prolog libraries.

  o INCLUDEDIR is used if you want to use YAP as a library.

  o INFODIR is where the info help files will be stored. It defaults
to $(SHAREDIR)/info.

3.2 Which YAP to compile

Compiling YAP with the standard options give you a plain vanilla
Prolog. You can tune YAP to use extra functionality by using the
following options to configure:

Compilation options:

 o --enable-depth-limit=yes allows depth limited evaluation, say for
implementing iterative deepening. It is required by the ILP system

 o --enable-use-malloc=yes makes YAP use the system's C-library
 allocation routines for all memory allocation. It is not compatible
 with save and restore.

 o --enable-threads=yes enables POSIX thread support.

 o --enable-pthread-locking=yes always use POSIX p-thread routines for locking.

 o --enable-low-level-tracer=yes allows support for tracing all calls,
retries, and backtracks in the system. This can help in debugging your
application, but results in performance loss.

 o --enable-wam-profile=yes allows profiling of abstract machine
instructions. This is useful when developing YAP and will not be very
useful for normal users.

 o --enable-tabling=yes allows tabling support.

 o --enable-or-parallelism={env-copy,sba,a-cow} allows or-parallelism
supported by one of these three forms. This is experimental.

 o --enable-dynamic-loading compile YAP as as a shared library.

 o --enable-win64 compile YAP as a WIN64 application.

 o --enable-cygwin compile YAP as a CYGWIN environment application, and not as stand-alone application.

 o --with-cudd=CUDD_PATH enable support of the CUDD library, used by
 packages such as ProbLog. Usually CUDD has to compiled from source
 (, but Fedora and MacPorts have
 cudd packages. In the case of Fedora, install cudd-dev and use
 --with-cud=/usr, in the case of MacPorts install cudd-dev and use

 o --with-gmp=GMP_PATH provide a path for GMP, in case GMP is not
 installed in the system. In a Linux machine, make sure you have
 installed the gmp-dev package. Binary versions of GMP are available
 for WIN32.

Functionality options:

 o --with-java=JAVA_PATH activates the Java Interface Library JPL. In
 Linux and WIN32 you have to provide a path to the Java library, in
 OSX it is sufficient to say yes.

 o --enable-condor compile YAP as a static program that can be run by condor

 o --enable-chr install CHR (enabled by default, if CHR is available)

 o --enable-clpqr install CLPQR (enabled by default, if CLPQR is available)

 o --enable-myddas install the MYDDAS MYSQL and/or ODBC interface
 package. YAP tries to compile this by default, if the odbc or MySql
 development files can be found.

 o --with-matlab install the MATLAB interface (not default). You need
 to provide the full path of the MATLAB install.

 o --with-mpi install the MPICH based MPI interface. This is default,
 if the development libraries can be found.

 o --with-mpe install the MPE interface.

 o --with-lam install the MPI LAM-based interface.

3.3 Porting YAP

The system has been mainly tested with GCC, but we have been able to
compile older versions of YAP under lcc in Linux, Sun's cc compiler,
IBM's xlc, SGI's cc, HP's cc, and Microsoft's Visual C++ 6.0. Recent
versions of YAP have also been compiled using Intel's lcc.