<<>>
<<CrankDealer.slides>>
<<Copyright Ó 1991 by Xerox Corporation.  All rights reserved.>>
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Crank Dealer
June 24, 1987
Crank and Grinder
f Motivation
Want to translate the Imager into Common Lisp
Cedar => Common Lisp hand translation tedious
f Crank reads sources, produces decorated trees
Written in Cedar
Uses the Interpreter's parser to build ASTs
Does (imperfect) type analysis
Writes Lisp-readable decorated trees
f Grinder
Written in Lisp
Reads trees produced by Crank
Writes (imperfect) Common Lisp
Example Source
    DIRECTORY
        IO USING [STREAM, ROPE, ROS, PutChar, RopeFromROS],
        Rope;

    CrankExampleImpl: CEDAR PROGRAM
    IMPORTS IO, Rope = BEGIN OPEN IO;

        Reverse: PROC [a: ROPE] RETURNS [ROPE] = {
            s: STREAM = ROS[];
            FOR i: INT DECREASING IN [0..Rope.Size[a]) DO
                s.PutChar[a.Fetch[i]]
                ENDLOOP;
            RETURN [RopeFromROS[s]]
            };

    END.
Example Abstract Syntax Tree
(:decl (:CONSTANT :TRUE)  
(:id () "Reverse")  
(:procTC (:SAFE :TRUE)  
(:decl ()  (:id () "a")  (:id () "ROPE")  NIL)  
(:decl ()  NIL  (:id () "ROPE")  NIL))  
(:body (:CHECKING :CHECKED)  
NIL  
(:decl (:CONSTANT :TRUE)  
(:id () "s")  
(:id () "STREAM")  
(:apply ()  (:id () "ROS")  NIL))  
(:list ()  
(:do ()  
(:downthru ()  
(:decl ()  (:id () "i")  (:id () "INT")  (:cast ()  NIL))  
(:intCO ()  
(:mwconst ()  (:literal () 0))  
(:apply ()  (:dot ()  (:id () "Rope")  (:id () "Size"))  (:id () "a")))  
NIL)  
NIL  
NIL  
(:apply ()  
(:dot ()  (:id () "s")  (:id () "PutChar"))  
(:apply ()  (:dot ()  (:id () "a")  (:id () "Fetch"))  (:id () "i")))  
NIL  
NIL)  
(:return ()  (:apply ()  (:id () "RopeFromROS")  (:id () "s"))))  
NIL))  
Example Decorated Tree
(:decl (:TYPECLASS :PROC :CONSTANT :TRUE)  
(:id (:QUAL "CrankExampleImpl") "Reverse")  
(:procTC (:SAFE :TRUE)  
(:decl (:TYPECLASS :REF)  (:id () "a")  (:id (:QUAL "IO") "ROPE")  NIL)  
(:decl (:TYPECLASS :REF)  NIL  (:id (:QUAL "IO") "ROPE")  NIL))  
(:body (:CHECKING :CHECKED)  
NIL  
(:decl (:TYPECLASS :REF :CONSTANT :TRUE)  
(:id () "s")  
(:id (:QUAL "IO") "STREAM")  
(:FUNCTIONAPPLY (:FIELDNAMES ("oldStream"))  
(:id (:QUAL "IO") "ROS")  
NIL))  
(:list ()  
(:do ()  . . . )
(:return ()  
(:FUNCTIONAPPLY (:FIELDNAMES ("self" "close"))  
(:id (:QUAL "IO") "RopeFromROS")  
(:id () "s"))))  
NIL))  
Example Decorated Tree (cont.)
(:do ()  
(:downthru ()  
(:decl (:TYPECLASS :INT32)  
(:id () "i")  
(:id () "INT")  
(:cast ()  NIL))  
(:intCO ()  
(:mwconst ()  (:literal () 0))  
(:FUNCTIONAPPLY (:FIELDNAMES ("base"))  
(:INTERFACESELECT (:SLOTNUMBER 15)  
(:id () "Rope")  
(:id (:QUAL "Rope") "Size"))  
(:id () "a")))  
NIL)  
NIL  
NIL  
(:FUNCTIONAPPLY (:FIELDNAMES ("char"))  
(:FUNKYAPPLY (:FROMINTERFACE "IO")  
(:id () "s")  
(:id (:QUAL "IO") "PutChar"))  
(:FUNCTIONAPPLY (:FIELDNAMES ("index"))  
(:FUNKYAPPLY (:FROMINTERFACE "Rope")  
(:id () "a")  
(:id (:QUAL "Rope") "Fetch"))  
(:id () "i")))  
NIL  
NIL)  
Data structures
f Attributed Tree
Like tree from interpreter parser, but with a place to add attributes for each name.
f Context
Stack of SymTab.Ref, keyed by identifier
Entries consist (mainly) of type code and qualifier
f Type table
Hash table, keyed by integer type codes
Entries describe the type, possibly in terms of other types
Not canonicalized (2360 entries for the example)
Type codes may be allocated before values are fully defined (to solve use-before-definition)
f Static value table
Not implemented
Cranking Interfaces
f The Crank always uses the source code
never .bcd files or Abstract Machine calls
f Caches (in memory) the result
f Uses fairly simple search rules
Local directory first, then version map
f Has to get through nasty low-level interfaces

[IO from [Cedar]<Cedar7.0>IO>IO.mesa!5
[Ascii from [Cedar]<Cedar7.0>Rope>Ascii.mesa!3
End Ascii ]
[Atom from [Cedar]<Cedar7.0>SafeStorage>Atom.mesa!3
[Rope from [Cedar]<Cedar7.0>Rope>Rope.mesa!3
[Basics from [Cedar]<Cedar7.0>MesaRuntime>Basics.mesa!6
[PrincOps from [Cedar]<Cedar7.0>MesaRuntime>PrincOps.mesa!8
  Error: Could not do this coercion
  Error: Could not do this coercion
  Error: Could not do this coercion
"[Cedar]<Cedar7.0>MesaRuntime>PrincOps.mesa!8|476"
    <<ShortPointer: TYPE = ORDERED POINTER [0..CARDINAL.LAST];>>
End PrincOps ]
End Basics ]
End Rope ]
End Atom ]
[BasicTime from [Cedar]<Cedar7.0>BasicTime>BasicTime.mesa!4
End BasicTime ]
End IO ]

What else might it good for?
(with more work)
f Cleaning up Cedar programs
removing nasty OPENs
removing (or adding) "object" notation
prettyprinting
changing positional <=> keyword notation
Checking for things the Compiler ignores
PUBLIC things that are not exported
use-before-initialization
unused types, variables, procedures
f Isosemantic editing
Globally renaming field names, reordering parameters.
f Crib sheet for Saffron implementation
Easier to read than compiler code (?)
However, not complete or correct