I'd be happy to see (1) made as a pull request.  (Doing it this way gets the 
Travis CI to automatically check it (at least to some extent).)

I agree that (2) is a useful distinction to make. 

Michael



On 30/8/18, 23:27, "Fabian Immler" <fimm...@cs.cmu.edu> wrote:

    Dear HOL4 Developers,
    
    In a recent thread on this list, Makarius mentioned experiments to load 
    HOL4 in the Isabelle Prover IDE. I participate in such experiments to 
    load HOL4 with Isabelle/HOL as kernel.
    
    Anyhow, some of the main obstructions concern references (type 'a ref in 
    SML).
    
    1) In a couple of places, the HOL4 code uses ref matching (i.e., ref is 
    used as a pseudo constructor that dereferences the cell).
    Would you mind converting those to explicit dereference operations? E.g. 
    according to (or pulling) changeset [1]?
    
    Such a change would make it easier to abstract over the concrete 
    implementation of reference cells.
    
    
    2) It seems like type 'a ref is used with (at least) two different 
    intended meanings: one, to track global state variables and two, for 
    private program variables.
    
    It seems like Isabelle/ML's module for thread-local data (that you 
    recently incorporated [2]) could be used for the first (global) meaning, 
    and 'a ref could be retained for private variables.
    
    Would you support distinguishing those different usages in one way or 
    another?
    
    Best regards,
    Fabian
    
    [1] https://github.com/immler/HOL/commit/b3ae0ef
    [2] 
    
https://github.com/HOL-Theorem-Prover/HOL/blob/1e8573d/src/portableML/poly/fromIsabelle/thread_data.ML
    
    
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