The SML/NJ Library Reference Manual


The ATOM signature

The Atom structure provides hashed strings with fast equality testing.


Synopsis

signature ATOM
structure Atom : ATOM

Interface

type atom
val atom : string -> atom
val toString : atom -> string
val sameAtom : (atom * atom) -> bool
val compare : (atom * atom) -> order
val hash : atom -> word

Description

type atom
Atoms are hashed strings that support fast equality testing.

atom s
creates an atom out of the string s. Two calls to atom with the same argument will return the same atom.

toString at
returns the string that the atom at was created from.

sameAtom (at1, at2)
returns true, if the two atoms are the same. This is a constant-time equality test.

compare (at, at2)
returns the relative order of the two atoms according to some internal ordering. Note that this is not the lexical ordering of the string representations of the atoms.

hash at
returns a hash value for the atom at.


See Also

AtomMap, AtomSet, AtomTable

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Last Modified May 29, 1996
Copyright © 1996 AT&T Research