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[smlnj] Diff of /sml/trunk/NOTES/HISTORY
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Diff of /sml/trunk/NOTES/HISTORY

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revision 665, Fri Jun 16 04:43:57 2000 UTC revision 666, Fri Jun 16 08:27:00 2000 UTC
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12  Tag: <post-commit CVS tag>  Tag: <post-commit CVS tag>
13  Description:  Description:
14  ----------------------------------------------------------------------  ----------------------------------------------------------------------
15    Name: Matthias Blume
16    Date: 2000/06/16 17:30:00 JST
17    Tag: blume-20000616-anchorenv
18    Description:
19    
20    This patch implements the long anticipated (just kidding :) "anchor
21    environment" mechanism.  In the course of doing this, I also
22    re-implemented CM's internal "SrcPath" module from scratch.  The new
23    one should be more robust in certain boundary cases.  In any case, it
24    is a lot cleaner than its predecessor (IMHO).
25    
26    This time, although there is yet another boot file format change, I
27    kept the unpickler backward-compatible.  As a result, no new bootfiles
28    are necessary and bootstrapping is straightforward.  (You cannot read
29    new bootfiles into an old system, but the other way around is no
30    problem.)
31    
32    Visible changes:
33    
34    ** 1. The $<singlearc> abbreviation for $/<singlearc> for anchored
35    paths has finally vanished.
36    
37    John had critizised this as soon as I originally proposed and
38    implemented it, but at that time I did not really deeply believe
39    him. :) Now I came full-circle because I need the $<singlearc> syntax
40    in another place where it cannot be seen as an abbreviation for
41    $/<singlearc>.  To avoid the confusion, $<singlearc> now means what it
42    seems to mean (i.e., it "expands" into the corresponding anchor
43    value).
44    
45    However, when paths are used as members in CM description files, it
46    continues to be true that there must be at least another arc after the
47    anchor.  This is now enforced separately during semantic analysis
48    (i.e., form a lexical/syntactical point of view, the notation is ok.)
49    
50    ** 2. The "cm" class now accepts an option "bind".  The option's value
51    is a sub-option list of precisely two items -- one labeled "anchor"
52    and the other one labeled "value".  As you might expect, "anchor" is
53    used to specify an anchor name to be bound, and "value" specifies what
54    the anchor is being bound to.
55    
56    The value must be a directory name and can be given in either standard
57    syntax (including the possibility that it is itself an anchored path)
58    or native syntax.
59    
60    Examples:
61    
62       foo.cm (bind:(anchor:bar value:$mystuff/bar))
63       lib.cm (bind:(anchor:a value:"H:\\x\\y\\z"))  (* only works under windows *)
64    
65    and so on.
66    
67    The meaning of this is that the .cm-file will be processed with an
68    augmented anchor environment where the given anchor(s) is/are bound to
69    the given values(s).
70    
71    The rationale for having this feature is this: Suppose you are trying
72    to use two different (already stable) libraries a.cm and b.cm (that
73    you perhaps didn't write yourself).  Further, suppose each of these
74    two libraries internally uses its own auxiliary library $aux/lib.cm.
75    Normally you would now have a problem because the anchor "lib" can not
76    be bound to more than one value globally.  Therefore, the project that
77    uses both a.cm and b.cm must locally redirect the anchor to some other
78    place:
79    
80       a.cm (bind:(anchor:lib value:/usr/lib/smlnj/a-stuff))
81       b.cm (bind:(anchor:lib value:/usr/lib/smlnj/b-stuff))
82    
83    This hard-wires $lib/aux.cm to /usr/lib/smlnj/a-stuff/aux.cm or
84    /usr/lib/smlnj/b-stuff/aux.cm, respectively.
85    
86    Hard-wiring path names is a bit inflexible (and CM will verbosely warn
87    you when you do so at the time of CM.stabilize).  Therefore, you can
88    also use an anchored path as the value:
89    
90      a.cm (bind:(anchor:lib value:$a-lib))
91      b.cm (bind:(anchor:lib value:$b-lib))
92    
93    Now you can globally configure (using the usual CM.Anchor.anchor or
94    pathconfig machinery) bindings for "a-lib" and "b-lib".  Since "lib"
95    itself is always locally bound, setting it globally is no longer
96    meaningful or necessary (but it does not hurt either).  In fact, "lib"
97    can still be used as a global anchor for separate purposes.  As a
98    matter of fact, one can locally define "lib" in terms of a global
99    "lib":
100    
101      a.cm (bind:(anchor:lib value:$lib/a))
102      b.cm (bind:(anchor:lib value:$lib/b))
103    
104    ** 3: The encoding of path names has changed.  This affects the way
105    path names are shown in CM's progress report and also the internal
106    protocol encoding used for parallel make.
107    
108    The encoding now uses one or more ':'-separated segments.  Each
109    segments corresponds to a file that has been specified relative to the
110    file given by its preceding segment.  The first segment is either
111    relative to the CWD, absolute, or anchored.  Each segment itself is
112    basically a Unix pathname; all segments but the first are relative.
113    
114    Example:
115    
116       $foo/bar/baz.cm:a/b/c.sml
117    
118    This path denotes the file bar/a/b/c.sml relative to the directory
119    denoted by anchor "foo".  Notice that the encoding also includes
120    baz.cm which is the .cm-file that listed a/b/c.sml.  As usual, such
121    paths are resolved relative to the .cm-files directory, so baz.cm must
122    be ignored to get the "real" pathname.
123    
124    To make this fact more obvious, CM puts the names of such "virtual
125    arcs" into parentheses when they appear in progress reports. (No
126    parentheses will appear in the internal protocol encoding.)  Thus,
127    what you really see is:
128    
129      $foo/bar/(baz.cm):a/b/c.sml
130    
131    I find this notation to be much more informative than before.
132    
133    Another new feature of the encoding is that special characters
134    including parentheses, colons, (back)slashes, and white space are
135    written as \ddd (where ddd is the decimal encoding of the character).
136    
137    ----------------------------------------------------------------------
138  Name: Allen Leung  Name: Allen Leung
139  Date: 2000/06/15 00:38:00  Date: 2000/06/15 00:38:00
140  Tag: leunga-20000615-x86-peephole  Tag: leunga-20000615-x86-peephole

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