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From: sher@rochester.UUCP
Newsgroups: net.lang
Subject: Re: Proc types
Message-ID: <19401@rochester.ARPA>
Date: Mon, 14-Jul-86 14:03:17 EDT
Article-I.D.: rocheste.19401
Posted: Mon Jul 14 14:03:17 1986
Date-Received: Mon, 14-Jul-86 22:35:08 EDT
References: <800016@ccvaxa>
Reply-To: sher@rochester.UUCP (David Sher)
Organization: U of Rochester, CS Dept, Rochester, NY
Lines: 35
Keywords: Enumerated types

This is in response to an article that requested an ability to have
types that pointed to a particular set of proceedures.  I would think
an even more useful artifact would be a type constructor that took
a set of elements of a particular type and had a type that only allowed
those elements.  Many languages now allow such for integers.  Thus
Now we have type constructors of the form:
array [a..b] of type
record of { t1 , t2 , t3 ... }
function from { t1 , t2 , t3 ...} to type

and variants thereof with various protections such as classes and
what not.  I suggest another type constructor:
enumeration from type of { e1 , e2 , e3 ...}

where ei is an element of type.  Thus you could have the pascal like
enumeration from int of { 1 , 5 , 7 , 12 }

or interestingly
enumeration from char * of { "GOOD" , "BAD" , "INDIFFERENT" }

or
enumeration from real of { 1.34273 , 123408.24398 , 23408 }

or
enumeration from int * ( int * x ) of { qsort , slowsort , merge }

Does any language have such a feature.  I think the semantics should be
non controversial.  The implementation however may cause some problem.

-David

-- 
-David Sher
sher@rochester
seismo!rochester!sher