Category: Pascal

Pascal: parameters by reference

I posted some time ago about Pascal, and the nice (and worst) things that Pascal has in its language. I discovered yet another cool thing. Unlike C, where you can pass parameters to functions by value, or using a pointer (and therefore, as reference), in Pascal you can use a value, you can use a pointer, or declare a parameter as a variable. This is similar to passing by pointer, but with a cleaner syntax.

Note the difference between

  1. procedure foo(bar: integer);
  2.    begin
  3.        bar := 10;
  4.    end;

and

  1. procedure foo(var bar: integer);
  2.   begin
  3.      bar := 10;
  4.   end;

The first procedure does not change anything in the outside world, while the second changes the value of the variable passed as argument.

As expected, the compiler raises an error if you call this second procedure with a constant integer.

Pascal: The Good, the Bad and the Ugly

As I posted before, I am teaching Pascal. I could discuss the relevance on teaching this language in this decade, but that is not my concern. I would like just to point The Good, the Bad and the Ugly I find in Pascal.

The Good: Pascal evolved and is a high level language. You have auto-growing strings (ok, with a size limit), you have arrays indexed by characters, integers or enumerated data types. That is good!

The Bad: Pascal syntax continues to be a mess. Begin and End keywords make the code big, the attribution with ‘:=’ makes it easy to type errors, and the low precedence of logic operators make me angry.

The Ugly: I can’t find a clean way to try opening a file without crashing the application. The only method I found (check the bottom of http://www.learn-programming.za.net/programming_pascal_learn10.html needs you to turn on and off compiler flags. That is annoying, stupid and decidedly too low level…

Pascal is not dead

Probably you know that I was a teacher at the Computer Science Department at Universidade do Minho. There I was a C and Perl teacher, as well as other classes that are not relevant for this post. Now, I am working at Instituto Politécnico do Porto, in the Escola Superior de Estudos Industriais e de Gestão. I am not responsible for the class, so I teach what the responsible teacher says. I was quite surprised they still used Pascal.

But this was a stupid question. Now, after getting back to the Pascal world, I noticed Pascal is not dead, and it getting better, and quite far from C when regarding the abstraction layer. I will not discuss efficiency. It I would do that, I would not program Perl anymore.

Pascal is, like C, a compiled language. But it supports growing strings. Strings can be edited as if they were Perl strings. You can add substrings to the string, remove substrings by nothing or other smaller or bigger strings. But you can also use it as an array of characters and access to each character individually. I really miss this feature in Perl.

Pascal is now supporting units as classes. This means it can be programmed as if it were an Object Oriented language. I did not get to that point yet. But it is nice to know Pascal evolved.

Oh, there is a free compiler (free pascal compiler) and there is an IDE (lazarus) that enables GUI application development just like the old Delphi.