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From: jls@rutabaga.Rational.COM (Jim Showalter)
Newsgroups: comp.object,comp.lang.misc
Subject: Re: Readability of Ada
Message-ID: <jls.672370717@rutabaga>
Date: 23 Apr 91 01:38:37 GMT
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%I think that it is interesting to note that the example used in this
%debate about the readability of Ada/C/C++ is in the domain where the
%solutions are essentially equivalent.

Do you honestly regard the C solutions as being as readable as the
Ada solution?

>I think that there is a significant issue in the readability of code
>where a language supports or fail to support a programming paradigm.

You mean like multi-thread execution not being supported by C++? ;-)

%So, how about comparing the languages on the example originally used
%to introduce the technique we now commonly refer to as object-oriented
%programming in the Simula textbook SIMULA BEGIN? The problem is to
%write a little program that define a set of shapes and manipulates
%them (I'll rotate a list of shapes). Then we add another shape and
%see what effort that takes and whether the original code manipulates
%shapes still works. There are other `tests' for object orientation
%(both harder and easier on the expressiveness of programming languages),
%but this one has the property of demonstrating a realistic problem
%of program organization in a small problem and has been around for
%about 20 years.

I've been wanting to ask someone who purports to know the answer
this question for over a year.

Consider the shapes example. Suppose that the given example goes
out in binary form, and arrives at my site, and I want to add a new
shape. Suppose that the initial shapes were limited to triangles and
squares. Suppose that I now add a Circle, which has a new method
defined for it that does NOT apply to triangles or squares and which
was never previously defined in the base class for shapes--radius.
This method returns the radius as some floating point number from 0
to whatever.

Now, I want to take a heterogeneous list of shapes, including triangles,
circles, and squares, and I want to iterate over the list and print
out all of the radii.

How do I do this? I can't get elements out of the list and call
the Radius method on all of them, because not all of them HAVE such
a method defined. I can't add the new method to the base class (with
a null implementation as the default for those shapes for which it
is a meaningless operation) because the base class is in binary. I 
can't ask the shapes to tell me their Kind because there is no such
operation defined on them in C++.

It is my claim that solving this problem in C++ results in a solution
that is every bit as messy as simply using a discriminated record
and an enumeration type in Ada--and Ada doesn't HAVE inheritance.
--
* The opinions expressed herein are my own, except in the realm of software *
* engineering, in which case I borrowed them from incredibly smart people.  *
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