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From: barmar@think.COM (Barry Margolin)
Newsgroups: comp.lang.ada,comp.lang.c
Subject: Re: "C" vrs ADA
Message-ID: <8022@think.UUCP>
Date: Tue, 1-Sep-87 18:03:42 EDT
Article-I.D.: think.8022
Posted: Tue Sep  1 18:03:42 1987
Date-Received: Sat, 5-Sep-87 04:47:54 EDT
References: <1065@vu-vlsi.UUCP> <2231@cbmvax.UUCP> <36@sarin.UUCP> <1678@rti.UUCP> <1963@sfsup.UUCP>
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Reply-To: barmar@godot.think.com.UUCP (Barry Margolin)
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Organization: Thinking Machines Corporation, Cambridge, MA
Xref: mnetor comp.lang.ada:628 comp.lang.c:4103
List-Id: <comp.lang.ada>

In article <1963@sfsup.UUCP> mpl@sfsup.UUCP (M.P.Lindner) writes:
>In article <1678@rti.UUCP>, jb@rti.UUCP writes:
>]    generic
>]       type ITEM is private;
>]       with function GREATER(A,B : ITEM) return BOOLEAN is <>;
>]    package SORTING is
>] 
>]       type VECTOR is array(NATURAL range <>) of ITEM;
>] 
>]       procedure MERGE_SORT( A, B : VECTOR; RESULTS : out VECTOR );
>] 
>]    end SORTING;

>But if I have to make a GREATER function I could have done it in C (see man
>page for qsort(3)!  Therefore I maintain my claim that Ada is *not* a proper
>implementation of an object oriented language (like Smalltalk).

Wait a second.  How can you write a generic sort in any language
without requiring that there be an ordering predicate for the element
type?

This is not like qsort(3).  Qsort requires that the ordering predicate
be specified in the call.  The above Ada code merely specifies that
the generic may only be instantiated for types for which GREATER (A,B:
type) is defined.  Smalltalk and Flavors have the same requirement,
but they don't notice the missing method until runtime.

---
Barry Margolin
Thinking Machines Corp.

barmar@think.com
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