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	revision 901, Tue Aug 14 19:21:17 2001 UTC	revision 902, Wed Aug 15 21:17:05 2001 UTC
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15	----------------------------------------------------------------------	----------------------------------------------------------------------
16	Name: Matthias Blume	Name: Matthias Blume
17		Date: 2001/08/15 17:15:00 EDT
18		Tag: blume-20010815-compreorg
19		Description:
20
21		This is a first cut at reorganizing the CM libraries that make up the
22		core of the compiler.  The idea is to separate out pieces that could
23		be used independently by tools, e.g., the parser, the typechecker, etc.
24
25		The current status is a step in this direction, but it is not quite
26		satisfactory yet.  Expect more changes in the future.
27
28		Here is the current (new) organization...
29
30		What used to be $smlnj/viscomp/core.cm is now divided into
31		six CM libraries:
32
33		$smlnj/viscomp/basics.cm
34		/parser.cm
35		/elabdata.cm
36		/elaborate.cm
37		/execute.cm
38		/core.cm
39
40		The CM files for these libraries live under src/system/smlnj/viscomp.
41		All these libraries are proxy libraries that contain precisely
42		one CM library component.  Here are the locations of the components
43		(all within the src/compiler tree):
44
45		Basics/basics.cm
46		Parse/parser.cm
47		ElabData/elabdata.cm
48		Elaborator/elaborate.cm
49		Execution/execute.cm
50		core.cm
51
52		[This organization is the same that has been used already
53		for a while for the architecture-specific parts of the visible
54		compiler and for the old version of core.cm.]
55
56		As you will notice, many source files have been moved from their
57		respective original locations to a new home in one of the above
58		subtrees.
59
60		The division of labor between the new libraries is the following:
61
62		basics.cm:
63		- Simple, basic definitions that pertain to many (or all) of
64		the other libraries.
65		parser.cm:
66		- The SML parser, producing output of type Ast.dec.
67		- The type family for Ast is also defined and exported here.
68		elabdata.cm:
69		- The datatypes that describe input and output of the elaborator.
70		This includes types, absyn, and static environments.
71		elaborator.cm:
72		- The SML/NJ type checker and elaborator.
73		This maps an Ast.dec (with a given static environment) to
74		an Absyn.dec (with a new static environment).
75		- This libraries implements certain modules that used to be
76		structures as functors (to remove dependencies on FLINT).
77		execute.cm:
78		- Everything having to do with executing binary code objects.
79		- Dynamic environments.
80		core.cm:
81		- SML/NJ-specific instantiations of the elaborator and MLRISC.
82		- Top-level modules.
83		- FLINT (this should eventually become its own library)
84
85		Notes:
86
87		I am not 100% happy with the way I separated the elaborator (and its
88		data structures) from FLINT.  Two instances of the same problem:
89
90		1. Data structures contain certain fields that carry FLINT-specific
91		information.  I hacked around this using exn and the property list
92		module from smlnj-lib.  But the fact that there are middle-end
93		specific fields around at all is a bit annoying.
94
95		2. The elaborator calculates certain FLINT-related information.  I tried
96		to make this as abstract as I could using functorization, but, again,
97		the fact that the elaborator has to perform calculations on behalf
98		of the middle-end at all is not nice.
99
100		3. Having to used exn and property lists is unfortunate because it
101		weakens type checking.  The other alternative (parameterizing
102		nearly *everything*) is not appealing, though.
103
104		I removed the "rebinding =" warning hack because due to the new organization
105		it was awkward to maintain it.  As a result, the compiler now issues some of
106		these warnings when compiling init.cmi during bootstrap compilation. On
107		the plus side, you also get a warning when you do, for example:
108		val op = = Int32.+
109		which was not the case up to now.
110
111		I placed "assign" and "deref" into the _Core structure so that the
112		code that deals with the "lazy" keyword can find them there.  This
113		removes the need for having access to the primitive environment
114		during elaboration.
115
116		----------------------------------------------------------------------
117		Name: Matthias Blume
118	Date: 2001/08/13	Date: 2001/08/13
119	Tag: blume-20010813-closures	Tag: blume-20010813-closures
120	Description:	Description:

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