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About Poly/ML

Table of Contents

  1. History and Acknowledgements
  2. How much of Standard/ML does Poly/ML support?
  3. What else does Poly/ML provide?
  4. Will Poly/ML run on my computer?
  5. What is the persistent store (version 4)?
  6. How do I use X-Windows/Motif in Linux?
  7. How do I make a stand-alone application?
  8. How do I stop abstract types from being printed in version 5.3?

History and Acknowledgements

Poly/ML was originally written by David Matthews at the Computer Laboratory at Cambridge University.  It was written in an experimental language, Poly, similar to ML but with a different type system.  Among the first users was Larry Paulson who used it to develop the Isabelle theorem prover.  It was licensed by Cambridge University's company Cambridge University Technical Services, then called Lynxvale, to Abstract Hardware Limited (AHL) who developed it further and used it to write the Lamba system for hardware verification as well as other tools.  Mike Crawley did significant work on the run-time system and Simon Finn was heavily involved in translating Poly/ML from Poly into Standard ML.  Nick Chapman (nic AT truthmachine DOT demon DOT co DOT uk) wrote the C-language interface. In 1999 AHL's rights in Poly/ML were acquired by CUTS and they agreed to make Poly/ML freely available.

More recently David Matthews has continued to develop Poly/ML. The Standard Basis Library has been implemented and the compiler converted to the 1997 Definition of Standard ML (Revised).  This work was supported in part by LFCS. The most recent work has been rewriting the run-time system which has resulted in the version 5 release. This work was supported by the Verisoft project and the Technical University of Munich.

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How much of Standard/ML does Poly/ML support?

Since the version 4.0 release Poly/ML now supports the full version of the language as given in the "Definition of Standard ML (Revised)", generally known as ML97.

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What else does Poly/ML provide?

As well as being extremely fast and efficient implementation of Standard ML Poly/ML provides several additional features.  There is a foreign language interface which allows dynamically linked libraries to be loaded and functions within them called from ML.   An X-Windows interface using Motif is available and a Windows programming interface.  There is also a symbolic debugger for Poly/ML.

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Will Poly/ML run on my computer?

Poly/ML is available for the most popular architectures and operating systems.   There are native code versions for the i386 (32 and 64 bit), Power PC and Sparc architectures.   There is a byte-code interpreted version which can be used on unsupported architectures. The configure script will automatically select the architecture when building from source.

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What is the persistent store (version 4)?

The persistent store (in version 4.2.0 and earlier) was a way of saving program state (the declarations made in an interactive session) from one session to the next.  Other implementations of Standard ML provide something similar.  The main differences are that Poly/ML uses memory-mapping to load the saved state into working memory rather than reading it in.   This greatly reduces the start-up time of a session and improves the virtual memory behaviour of the program as well as reducing the load on the garbage collector.

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How do I use X-Windows/Motif in Linux?

You need to build Poly/ML from source and provide the --with-x option to the configure script. Check that you have the appropriate X-Windows and Motif libraries installed first.

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How do I make a stand-alone application?

This was complicated in older versions of Poly/ML but as from version 5.0 you can simply export a function and link the resulting object file with the Poly/ML libraries..

$ poly
Poly/ML 5.0 Release
> fun f () = print "Hello World\n";
val f = fn : unit -> unit
> PolyML.export("hello", f);
val it = () : unit
> ^D
$ cc -o hello hello.o -lpolymain -lpolyml
$ ./hello
Hello World

The line that links with the libraries may need to be tweaked depending on the operating system. If you have installed the libraries in a directory that is not in the search path you may need to add this. For example
cc -o hello hello.o -L/usr/local/lib -lpolymain -lpolyml
It is possible to use the ld command rather than cc here but you may need to include some of the default C and C++ libraries on the command line. On some platforms it may be necessary to add some or all of -lstdc++, -lm, -ldl or -lpthread. On Cygwin you may need to use g++ instead of cc since that includes the appropriate C++ libraries.

On 64-bit Mac OS X you will also need -segprot POLY rwx rwx .

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How do I stop abstract types from being printed in version 5.3?

Earlier versions of Poly/ML printed values of abstract types and types in opaque signatures just as "?". From version 5.3 Poly/ML now prints the values using the constructors. To suppress this and return to the old behaviour you need to install a pretty-printer for the abstract type. The following code installs a pretty printer that always prints "?" for a type.

    fun pp _ _ (_: MY_TYPE) = PolyML.PrettyString "?"
    PolyML.addPrettyPrinter pp

Generally the best place to put this code is inside the implementation of the abstract type. This applies whether you are using an abstype or transparent or opaque signature matching to achieve your abstract type. It is also possible to install the pretty printer outside the abstract type and this will work equally well with abstype and transparent matching. With opaque signature matching you can also install the pretty printer outside the structure definition but in some circumstances, particularly if an exception is raised inside the implementation which contains the abstract type as a parameter, the value may be printed with the default printer instead.

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