Poly/ML May 2008

polyml@lists.polyml.org

9 participants
6 discussions

structure sharing
by ldixon＠inf.ed.ac.uk 02 Jul '08

02 Jul '08

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I've been trying to use the module system and come across a few issues, some of which I cannot easily pin down, and one which I can. The issue I can clearly identify concerns what seems to be failure of associativity in structure sharing, and is demonstrated in the following: signature ORD_DATA = sig type data end; signature VERTEX = sig type name type data end; signature BVERTEX = sig structure Boundary : ORD_DATA include VERTEX end; signature GRAPH = sig structure Vertex : VERTEX type T; end; signature BGRAPH = sig include GRAPH; structure BVertex : BVERTEX sharing Vertex = BVertex end; signature RG_VERTEX = sig include BVERTEX where type Boundary.data = unit end; signature RG_GRAPH = sig include BGRAPH structure RGVertex : RG_VERTEX sharing BVertex = RGVertex (* why is it OK if I change BVertex to Vertex? *) end Running this gives the error: Error: in '/tmp/sml25644bEn', line 26. Cannot share: (unit) is a type function Found near sig include BGRAPH structure RGVertex : RG_VERTEX sharing BVertex = RGVertex end Exception- Fail Static errors (pass2) raised Apart from just being confused by what the error means, I am confused that given, in BGraph, "sharing Vertex = BVertex", later I get an error if "BVertex = RGVertex" but not if "Vertex = RGVertex". Is there some subtle (or obvious?) thing I'm missing? Another thing I don't quite understand, but which I suspect is just part of the definition of ML, is that you cannot write "sharing type localtype = globaltype", is there some clever reason why this isn't allowed? Or even "sharing local_structure = global_structure", would sometimes be nice. :) The other issue I have is with the names given to types being printed in error messages; is there any way to control this? I sometimes seem to get mis-typed types; which makes errors hard to spot. A common thing I find is that a parameterised type loses it's parameter. I have example of this I can repeat, but they require a large amount of code... I'll try to find a smaller example. any suggestions/corrections/infomration, and possibly bug fixes, very welcome! :) cheers, lucas -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFINuQvogMqU4edHsMRAnq3AKDEOOZK6W4Yl9qLIybMvIYRmrGu8ACeKZIG 2RtB76HxIEiw+Kxd/xiYvGw= =mxpJ -----END PGP SIGNATURE-----

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Fwd: [polyml] Re: Interactive behaviour and ctrl-c
by David.Matthews＠prolingua.co.uk 31 May '08

31 May '08

Dear Tom, Your example is essentially doing nothing but growing the stack. The stack is held in the heap and whenever the current segment runs out a new, larger, segment is allocated and the current contents of the stack are copied into that. That can result in garbage collection. Both garbage collection and stack copying are non-interruptible so in either case an interrupt will be deferred until the action is complete. The handling of ctrl/C has been improved in the CVS version compared with the 5.1 release but there are still delays if ctrl/C is pressed during a garbage collection. While investigating this I did discover a bug that resulted in the garbage collector saying that there was insufficient space to extend the stack when in fact there was enough. It's likely now that your example would result in a Warning - Stack limit reached - interrupting process message since the stack will probably run out before the ctrl/C is processed. There may be more of a problem with the 64-bit version than the 32-bit version because the maximum size of a stack segment is larger in the 64-bit version so the limitation is likely to be the overall memory rather than the stack size. David Tom Ridge wrote: > Dear David, > > I just tried the following experiment in poly (see below). > > Under mosml, ctrl-c causes an almost instantaneous return to > top-level. Under poly, the time to return seems dependent on the depth > of recursion(!). Does this sound possible? Is there anyway to get poly > to raise the exception to toplevel in a more timely fashion? > > Thanks > > Tom > > ---------- Forwarded message ---------- > From: Tom Ridge <thomas.ridge(a)cl.cam.ac.uk> > Date: 2008/5/23 > Subject: Re: [polyml] Re: Interactive behaviour and ctrl-c > To: Michael Norrish <Michael.Norrish(a)nicta.com.au> > Cc: hol-developers(a)lists.sourceforge.net > > > Dear All, > > I've just tried this simple experiment in poly's top-level: > > --- > > fun f x = 1 + f x; > > f 1; > > (* leave this to run for 10 or 20 seconds *) > > (* type ctrl-c *) > > (* type f to raise an exception *) > > (* now wait while the exception is raised... this takes a while *) > > --- > > So it seems that the slow-ctrl-c behaviour is something to do with > (64bit) poly, and not HOL. Can someone confirm that this *doesn't* > happen under 32bit poly (linux and Mac). >

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Poly/ML syntax for constructors too liberal?
by rda＠lemma-one.com 13 May '08

13 May '08

Poly/ML correctly allows the following binding: val op :: (h, t) = [1, 2, 3, 4]; However it also allows brackets around the constructor: val (op ::) (h, t) = [1, 2, 3, 4]; My reading of the syntax in the definition of Standard ML is that the latter form should not be allowed. Am I right? Regards, Rob.

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Re: Interactive behaviour and ctrl-c
by thomas.ridge＠cl.cam.ac.uk 13 May '08

13 May '08

Just to follow up my previous post, the first problem also appears under mosml. The behaviour would result if the Interrupt exception were being caught during the proof step and not propagated. The tactic I am using is SIMP. Grepping the HOL sources reveals many places where an arbitrary exception is caught and not propagated. This would prevent Interrupts from being propagated. There has also been some effort to ensure that general exceptions are not caught (e.g. HOL_ERR is caught rather than a general exception). Given that there are many potential places in HOL where Interrupt could be caught and not thrown, is there any reason to believe that the HOL code is not wrong in these places? The second problem, where polyml loses the ability to call system functions, remains. T 2008/5/12 Tom Ridge <thomas.ridge(a)cl.cam.ac.uk>: > Dear All, > > I have been using HOL with Scott Owens' new port to polyml. To > interrupt a proof that takes a long time, I hit ctrl-c. I get the > polyml #> prompt straightaway. However, if I type f (raise an > exception) then nothing happens for a long while. This time seems to > increase the longer the interrupted proof step has been running. > > Eventually the system seems to return, but it is not clear whether an > exception has been raised or not. Certainly the goalstate is now > different. On the other hand, the goal state should not result if the > proof step completed (but this is likely some erroneous behaviour at > the HOL level). > > There is another problem though. The HOL/polyml top-level is usable > for cut-and-pasting. However, I can't invoke any commands that involve > system calls, otherwise I get a "Function system failed" message (from > libpolyml/process_env.cpp). This is a problem because the xemacs sml > mode writes commands to a temporary file and "use"s them into the > top-level. > > Does anyone have any ideas what might be causing these two problems? > > Thanks > > Tom >

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timing issue with polyml 5 on windows
by rdharrison2＠hotmail.co.uk 12 May '08

12 May '08

Hi all, = I've been running polyml 5.1 on windows from a C# application as a child pr= ocess, redirecting standard input/output via the startupinfo and am having = a timing performance problem... = I have found that when sending small SML commands to polyml (that take 10s = of milliseconds to execute) the output only comes back after about 500ms. T= his seems to be because threads in polyml on windows wait for 500ms = in Processes::ThreadPauseForIO before re-polling for input. Is this correct= , and if so can I get around this? (looking at the source code suggests I m= ay be able to send polyml a message to kick it into action at the appropria= te time?) = regards, Richard Harrison. = _________________________________________________________________ Be a Hero and Win with Iron Man http://clk.atdmt.com/UKM/go/msnnkmgl0010000009ukm/direct/01/-------------- = next part -------------- An HTML attachment was scrubbed... URL: http://lists.inf.ed.ac.uk/mailman/private/polyml/attachments/20080501/= d1d4d5a7/attachment.html

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Exception- Subscript unexpectedly raised while compiling
by ldixon＠inf.ed.ac.uk 11 May '08

11 May '08

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 While compiling a large program I came across the following rather strange error message: Exception- Subscript unexpectedly raised while compiling Exception- Fail "Exception- Subscript unexpectedly raised while compiling" raised After a bit of hacking I managed to reduce it to the following program: (which uses Isabelle's pretty printing library, and which I tested using Isabelle2007) fun foo l s x i = [] @ map (fn (i,s) => Pretty.block [(case x of NONE => Pretty.str "a" | SOME openi => (if (openi = i) then Pretty.str "b" else Pretty.str "c")), Pretty.str "d"]) l; This is running PolyML 5.1... is this a known issue fixed in more recent cvs snapshots? My workaround was to move the case statement into it's own function. Then it compiles ok. cheers, lucas -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iD8DBQFIIJ7ciUn2r+81A2gRAlswAJ4/zXeHsGEGYlghC5EwGiFoj3ikxACgpl/l ntaCRqc04AreddbBV/2yYZ8= =kQQi -----END PGP SIGNATURE-----

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Poly/ML May 2008