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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Warning: Religious naming convention discussion :-) [was: assign
 help!!]
Date: 1997/05/13
Message-ID: <EA4J04.LpH@world.std.com>#1/1
X-Deja-AN: 241286950
References: <5kjvcv$evt@news.cis.nctu.edu.tw> <dewar.863448507@merv>
 <EA33qK.KtA@world.std.com> <dewar.863495951@merv>
Organization: The World Public Access UNIX, Brookline, MA
Newsgroups: comp.lang.ada
Date: 1997-05-13T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <dewar.863495951@merv>, Robert Dewar <dewar@merv.cs.nyu.edu> wrote:
>Why are C arrays very low-level notions?

Because:

1. They don't carry their length (or bounds) with them.  You have to
pass this information "by hand", as a separate thing.

2. There are no "whole array" operations, such as assignment and
comparison.  (Yes, there are library functions for these, but they don't
operate on whole arrays -- they take pointer-to-first-element and
size/length parameters separately.)

3. You can't pass an array as a parameter -- you have to pass a pointer
to the first component, instead.  (Or, looking at it a different way, an
array *is* a pointer to the components.  C is pretty confused on this
point.)  And having done that, there's no way to tell, in the language,
whether a given formal parameter of type t* is pointing to a t, or to
the first element of an array of t's.

4. Array indexing is defined in terms of pointer arithmetic.
(Well, I admit this is a rather weak reason.)

5. The lower bound is always zero, rather than whatever makes sense to
the programmer.  E.g. if you want a table that maps the numbers A..B
onto something-or-other, you have to subtract off A "by hand"

All of the above give me the feeling that a C array is, conceptually, a
pointer to a hunk of contiguous storage.  That's a low-level,
machine-oriented, notion.

>I agree they are often used this way, but I don't see this from the standard.

- Bob