A Simple PROLOG Compiler to WAM
WAM (Warren Abstract Machine) is an efficient popular abstract machine to compile Prolog logic programs and is implemented in almost all industrial-strength PROLOG compilers such as SWI-Prolog and YAP.
This interpreter contains the compilation and runtime of WAM instructions based on the definition in Russinoff 1992. The interpreter is developed in Haskell and the purpose of the project is to be used as testbed for various extensions in WAM.
To build the WAM compiler you should have a system with GHC and cabal. The following sequence of commands will build the compiler after installing any dependencies needed.
$ cabal update $ cabal install --only-dependencies $ cabal configure && cabal build
Compile an example to WAM
After a successfull build the compiler will reside by default in
You can add the directory to your current path, i.e.
$ export PATH=`pwd`/dist/build/wam:$PATH
To compile a PROLOG program to WAM you should issue:
$ wam -c -i prog.pl -o output.wam
prog.pl is your initial PROLOG source file,
output.wam is the
name of the output file that will contain WAM bytecode. The switch
only compile the program but not run. On the other hand if you omit
$ wam -i prog.pl -o output.wam
the program will also be executed after the compilation.
Features and Limitations
Compilations supports some basic optimizations such as
- tail execution optimization
- unsafe variables
There are also some features of WAM that are not yet supported such as:
- There are no special instructions for lists (get_list, put_list).
- No environment trimming.
- No indexing at the switch-operators
- No cut functionality
- No garbage collection has been implemented.
- A subset of the ISO-Prolog is supported and compiled. No build-in predicates are supported, neither user-defined operators.