The Concurrent ML FAQ

Questions

  1. What version of SML/NJ should I use?
  2. How do I run a CML program?
  3. How do I compile a CML program?
  4. How do I use the SML/NJ Libary from a CML program?
  5. Can I use the top-level print function in a CML program?
  6. Can I use CML primitives at top-level?
  7. Why does Int.toString occassionally return the wrong result?

Answers

What version of SML/NJ should I use?

CML works with both the latest released version of SML/NJ (Version 110.0.7) as well as with recent working versions. Since the recent working releases of SML/NJ are quite solid, we recommend them over SML/NJ 110.0.7. If you choose to use 110.0.7, then you may want to update your copy of CML with a more recent version (also, see the note below).

How do I run a CML program?

It is not possible to execute CML code directly from the SML/NJ top-level loop; instead one must invoke the main thread of a CML program using the function RunCML.doit. For example, the following is a self-contained CML program:
structure Main = struct
  fun hi () = RunCML.doit (
        fn () => TextIO.print "hello world\n",
        SOME(Time.fromMilliseconds 10))
end
The second argument to RunCML.doit specifies the scheduling quantum; if you specify NONE, then the default quantum of 20 milliseconds is used.

How do I compile a CML program?

The recommended way to compile CML programs is to use the SML/NJ compilation manager (CM) and to include ``cml.cm'' in your project's CM file.

How do I use the SML/NJ Libary from a CML program?

Some of the modules in the SML/NJ Libary are not thread safe; therefore CML provides its own implementation of these library modules. To access modules from the SML/NJ Libary, include ``cml-lib.cm'' in your project's CM file.

Can I use the top-level print function in a CML program?

Yes, but your program must also include an explicit reference somewhere to the TextIO module. Without such a reference, the CML version of TextIO does not get loaded when your program is compiled and the print function resolves to the SML/NJ version; since this version of print is not thread safe, problems will result. The most frequent symptom is mysterious deadlock.

Can I use CML primitives at top-level?

Because channels, mailboxes, etc. that are bound at top-level (including top-level bindings in modules) persist across multiple runs of a CML program, they must be registered with the CML run-time to ensure that they are initialized each time RunCML.doit is called. The RunCML structure has functions for registering top-level channels and mailboxes.

Can I use CML on Windows?

CML has been ported to Windows (by Riccardo Pucella) and is installed as part of the standand Windows installation.

Why does Int.toString occassionally return the wrong result?

There is a bug in the way that the SML/NJ 110.0.7 compiler handles 32-bit integers across GC tests (they do not get preserved). This bug has also caused problems with file handles on Windows, which are represented by 32-bit words. This bug is not present in recent working versions.

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Last updated on October 9, 2002.
Comments to John Reppy.