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Date: -- (:)
From: Michael Ekstrand <michael@e...>
Subject: Re: Symbol type
On 06/27/2010 10:15 PM, José Romildo Malaquias wrote:
> Is there a symbol type in OCaml, with a constant time comparison
> function? Something like symbols from Scheme and LISP or atoms from
> Prolog. Useful in compiler construction.

Not directly.  As I see it, you have two decent options:

- Use/write a symbol table which "interns" symbols to integers.  The
resulting integers can be compared.
- Use/write a symbol table which interns symbols to unique string
instances, so SymTbl.intern "foo" returns the existing string object if
one already exists, and the string object passed in if it's never been
seen before.  The resulting strings can be compared with == rather than
= in constant time.

Either of these options would be fairly similar to how symbols work
under the hood in a Lisp implementation, I believe.

- Michael