0001284: Fix offered for "illegal stream concatenation" in Stream

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0001284

OCaml

OCaml general

public

2002-07-31 07:22

2012-06-09 13:07

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administrator

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Priority

normal

Severity

feature

Reproducibility

always

Status

closed

Resolution

fixed

Platform

OS Version

Product Version

Target Version

Fixed in Version

3.11.0

Summary

0001284: Fix offered for "illegal stream concatenation" in Stream

Description

The documentation in Stream.mli says:

   Warning: these functions create streams with fast access; it is illegal
   to mix them with streams built with [[< >]]; would raise [Failure]
   when accessing such mixed streams.

As an example of this, the following code fails:

   open Stream;;
   npeek 20 (iapp (of_string "as") (icons 'z' (of_list ['d'; 'f'])));;

(This is an artificial example. The actual example that motivated me
has since been replaced by a workaround, so I don't have it
conveniently available.)

The resolution of bug 235 at

   http://caml.inria.fr/bin/caml-bugs/not%20a%20bug?id=235;user=guest;selectid=235 [^]

reaffirms that this behavior is considered acceptable, but it doesn't make
sense to regard throwing an exception as better than computing a useful result.
I found it frustrating that the compiler wouldn't help me predict when a stream
operation would fail with the "illegal stream concatenation" error, so I
rewrote stream.ml so all streams are valid inputs to all stream operations that
take streams as arguments.

I plugged it into the ocaml source from anonymous CVS and the compiler
was able to bootstrap fine. It also passes a fairly thorough unit
test that's in the comments at the end, and it has reasonable
performance according to the benchmark at the end of the test cases.

Is there any interest in incorporating this changed code into OCAML?

The revised .ml file is at

   http://www.fungible.com/stream_fixed.ml [^]

and the .mli file (which is identical to the old version, except for a few
comments) is at

   http://www.fungible.com/stream_fixed.mli [^]

As indicated by the header at the beginning of stream_fixed.ml, I'm happy to
assign copyright on the rewritten file to INRIA if it gets incorporated into
OCAML.

--
Tim Freeman
tim@fungible.com
GPG public key fingerprint ECDF 46F8 3B80 BB9E 575D 7180 76DF FE00 34B1 5C78

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Relationships

parent of	0001289	closed		Speed improvement Stream replacement
related to	0005644	assigned	gasche	Stream.count broken when used with Sapp or Slazy nodes

Notes
(0006797) doligez (manager) 2012-01-25 15:50	This restriction was removed in 3.11.0 and the example now works (tested in 3.12.1). I am updating the documentation (stream.mli) by removing the paragraph in question. Problem fixed in 3.11.0 (commit 8893), documentation fixed in trunk (3.13.0) (commit 12077).

Issue History
Date Modified	Username	Field	Change
2005-11-18 10:13	administrator	New Issue
2012-01-25 15:50	doligez	Note Added: 0006797
2012-01-25 15:50	doligez	Status	acknowledged => closed
2012-01-25 15:50	doligez	Resolution	open => fixed
2012-01-25 15:50	doligez	Fixed in Version	=> 3.11.0
2012-01-25 15:50	doligez	Description Updated	View Revisions
2012-01-25 15:55	doligez	Relationship added	parent of 0001289
2012-06-09 13:07	gasche	Relationship added	related to 0005644