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Re: [Scheme-reports] Cycle detection problems: #442, #338, "equal?"

David A. Wheeler scripsit:

> Big-O hides the constants, which concern me.  And I see no eq-hash-table
> in the spec to do that anyway; did I miss it?  I didn't think
> R7RS had hash tables.  Without a portable hash table, many smaller
> implementations (especially if they want portability) are going to
> create sloooow list implementations.

In practice all Schemes have hash tables, if only to implement symbols,
and usually expose an interface for them.  The reason that the WG didn't
require implementations to expose hash tables is that we couldn't agree
on an interface.  R7RS-large will certainly provide a standard interface.

Note that having a portable implementation of R7RS `equal?` is not an
issue, as all implementations are expected to provide it.  They may also
(as Chibi does) also provide the R5RS `equal?` function in a different

Overhead, without any fuss, the stars were going out.
        --Arthur C. Clarke, "The Nine Billion Names of God"
                John Cowan <cowan@x>

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