How to compile picoProlog from source code?

Question

I am a student in Computer Science, and I am learning about logic programming with Prolog.

I have found an interesting Prolog interpreter, picoProlog (http://spivey.oriel.ox.ac.uk/corner/Logic_Programming).

To know more about Prolog, I am trying to compile their source code, but I failed.

In this web page, they said:

The interpreter source is written in a minimal dialect of Pascal, avoiding many features including pointers, but using macros to overcome some of Pascal's limitations, in a style inspired by Kernighan and Plauger's book Software tools in Pascal. It comes with a translator from the Pascal dialect into C that can be used to build the interpreter and also source for the macro processor that is needed.

To build the interpreter on a Linux machine, just extract the tar file and type make. The building happens in several stages:

1. First, the Pascal-to-C translator ptc is built from C source, including a lexer and parser written with lex and yacc. The file README gives some details of the very restricted Pascal subset accepted by this translator.
2. Next, ptc is used to build the macro processor ppp.
3. Finally, the picoProlog interpreter is built from the source code in the file pprolog.x by first expanding macros using ppp to obtain a file pprolog.p, then translating to C with ptc, and lastly compiling the C code.

Text and software copyright © J. M. Spivey, 1996, 2002, 2010.

They said about compiling on Linux only, so I don't know how to compile this source code in Windows machine. Can I compile it with Turbo Pascal 7.0 (without any requirement) on Windows XP? Can you remove some part of script for Pascal compiling only?

Answer 1

To avoid spending more time in getting the P2C/PTC bootstrapping to run while you are probably only interested in the interpreter and not its *nix bootstrapping, I think it is easier to forget the PTC stuff and focus getting the pascal parts to compile/work with FPC 2.6.x. (the below took 10 minutes), generating a standalone Windows EXE with 10-20 code line additions.

Start with ppp, hmm, that compiles (nand works!) out of the box:

D:\dls\prlg\pprolog>fpc ppp.p
Free Pascal Compiler version 2.6.2 [2013/02/12] for i386
Copyright (c) 1993-2012 by Florian Klaempfl and others
Target OS: Win32 for i386
Compiling ppp.p
Linking ppp.exe
394 lines compiled, 0.1 sec , 30352 bytes code, 1692 bytes data

The code does looks like it is meant to have its input piped in. We haul pprolog.x through it (ppp) and it (pprolog.pp) almost compiles. There are four problems, but all are fixable by adding some code to the top, and not changing original code (marked with MVDV: in the source)

1. Some range check errors because integer type is too small for the 1MB stackspace that is set up. This prohibits Turbo Pascal usage, but we can workaround it by defining integer as longint.
2. Seems it assumes that forward functions don't need their arguments repeated while in FPC they generally do, fixed.
3. In the final function of ("initialize") some non standard ptc library functions are used that borrow from C (argv, argc) instead of their typical pascal equivalents. Fixed.
4. (reported by original author after testing) ParseFactor has a right hand recursion that is substituted by reading the result. Enable TP mode ( {$mode tp} above the uses line), or add () to disambiguate

After these, pprolog.pp compiles with FPC:

Free Pascal Compiler version 2.6.2 [2013/02/12] for i386
Copyright (c) 1993-2012 by Florian Klaempfl and others
Target OS: Win32 for i386
Compiling pprolog.pp
pprolog.pp(487,19) Warning: unreachable code
pprolog.pp(532,19) Note: Local variable "dummy" is assigned but never used
Linking pprolog.exe
2150 lines compiled, 0.1 sec , 84400 bytes code, 13932 bytes data
1 warning(s) issued
1 note(s) issued

Some notes:

1. UNTESTED
2. I don't know if I got the range of argv/argc exactly right. (0..argc-1 while paramcount is 1-based etc) Check if necessary.
3. The string system predates the TP String type and is convoluted (probably because of PTC, see README), I don't know if it will work.

I've put the resulting, compiling source code at http://www.stack.nl/~marcov/files/pprolog.pp

Good luck!

Answer 2

Given how many different variations of Pascal have existed, my gut feeling is it's easier to get hold of a Linux environment than to adjust the Pascal source code to fit the compiler you have. And this is only the first step.

Getting a Linux environment? Try a virtualbox - https://www.virtualbox.org

Answer 3

I found this question while googling, and though it's old, I thought it would be helpful to add a definitive answer from the author of the program.

It is indeed not too hard to get picoProlog to compile with the Free Pascal Compiler. I've incorporated Marco's suggestions into the source, fixed a small bug that was revealed, and added a workaround for an odd feature of Free Pascal. The results can be found on the BitBucket page:

http://bitbucket.org/Spivey/pprolog

with instructions for building in the README.

Note: I built this with Free Pascal under Linux on x86_64, but haven't tested it on Windows. I can't see a reason why it wouldn't work.