Re: "Subtract C, add Ada"

[dobrien@seas.gwu.edu (David O'Brien)]

R.A.L Williams (bill@valiant) wrote:
: My experience of writing software and running software projects in C
: highlights four common low-level C errors:
:   1. = instead of == and vice versa

I have to wonder.  What if C defined the logical equals operator to be
"=" and the assignment operator to be ":=" just like Ada, Algol, Pascal,
Modula-x, etc?  Would this error still exist???

Quickly thinking about it, I feel that I write a lot more assignment
statements than local statements, couldn't I be in the habit of typing
":=" and thus accidently type that when I meant logical comparison?
Since that would still be a perfectly valid, conforming C program,
the compiler is not required to give any warnings (just like current
practice).  Thus, I would still have the same logic error in my program.
Chances of happening???  Any bodies guess.  So is the problem really
one of symbol choice, or program semantics?


:   2. spurious ; after for(...) or while(...)

This is one area I *really* like about Ada.  However, I feel there
is a much more common programming error (occurs in Pascal too):
     for (...)
	first_action();
	second_action();

The indenting implies that "second_action()" should be part of the
the loop body.  But it isn't.  :-))   So many times I've seen this
in industry.  Every new programmer I work with I try to drill into
their head's "*always* use braces with your if, while, for statements,
even when you have only one thing in your loop body.  For one day a
maintainer will need to add that second thing, and indent like the
above -- forgetting to add the braces."  Many will not listen thinking
they know better.  Tisk, tisk, tisk.  Usually it doesn't take long for
them to get bitten and remember.  Same for Pascal.  I really don't
understand why most languages are designed the Pascal/C way rather
than the Ada way.  Especially since it removes the common ambiguity
of nested if statements.

-- David O'Brien	(dobrien@seas.gwu.edu)