Some Thoughts On Programming Style

In QHJ #24 Tim talks about a colleague’s style of writing Perl and contrasts it with his own. I have spent several years as a programming and system development lecturer within my company’s internal training department and nothing seems to cause more grief/criticism/etc., etc., as differences of programming style.

I tend to use procedure calls in preference to the use of deep nesting of ‘if..then..else..endif’ structures as does Tim’s colleague. I do this for a number of reasons and even if the procedure may only be called once in the entire program (incidentally this approach is taken by Kernighan and Ritchie in ‘The C Programming Language’ and by Kernighan and Plauger in ‘Software Tools in Pascal’).

My reasons are these:

• it is sometimes inconvenient to read deeply nested ‘if..else..endif’ or ‘while..endwhile’ constructions;
• this approach works very well with the program design method that I prefer to use (Jackson Structured Programming, aka. JSP);
• if suitable procedure names are chosen the clarity of the code is often improved;
• the style is closer to the object-oriented programming approach that I would prefer to use;
• the arguments about inefficiency (“It’s wasteful to set up a stack frame and call code that could have been inline.”) take little account of the maintenance benefits that can accrue from well-designed and named procedures.

I find something like this much easier to follow (and debug!),

    procedure DoLotsOfThingsTo(var A : AType);

    var
         i : integer;

    procedure DoOneThingTo(var A : AType );

    begin
         A.A := ...;
         A.B := ...;
    end {DoOneThingTo};

    begin
         for i := 1 to SizeOfAType do
              DoOneThingTo(A);
         ...
    end {DoLotsOfThingsTo};

(the above also shows one reason that I like Pascal – the ability to nest procedure declarations – I miss it a lot when I use C, C++ or things like Visual Basic).

Incidentally, Question: can you nest procedure definitions in SuperBasic?

Answer: Yes you can:

    1000 define procedure testa
    1010 :
    1020 define procedure testb
    1030 print "In testb"
    1040 end define testb
    1050 :
    1060 print "In testa (1)"
    1070 testb
    1080 print "In testa (2)"
    1090 :
    1100 end define testa

works perfectly, printing out,

    In testa (1)
    In testb
    In testa (2)

as expected.

As I said in my article on parameters and parameter passing mechanisms I think that most languages would be better if they were designed so that procedures and functions (in the SB or Pascal sense) could only access local variables or parameters – even for read access only.