80-Bus News

  

November-December 1982, Volume 1, Issue 4











Page 10 of 51











10.

What is wrong with Pascal? (Shock Horror!)

Honestly, tnere really is one thing missing from Pascal, and it just happens that-this is the one thing BASIC is better at than almost anything else (that takes care of the ones I don’t know! PIC X(12), indeed!) String handling is easy in Pascal, as long as all the strings are the same length! You can not use things like

A$ = LEFT$(B$,4) + MID$(A$,3,3) + " Wowee!" even if you want to. But of course, you can define a set of procedures and functions that would make this sort of thing possible. I have started work on just such a set of procedures, and have made a little progress, some of it in the right direction...

It is necessary to learn how to use the "dynamic variables" of Pascal, as the other way of approaching the problem, using a huge array of characters, while probably faster, takes up memory all the time. That defeats one of the objects, so the dynamic approach it is. The things BASIC can do to its string variables include setting them to “empty”, concatenation, and the ever useful LEFT$, MID$ and RIGHT$. Also useful are the ability to type into a string from the keyboard, and to print strings out. Some sort of clue as to how difficult such things are to program in Pascal can be gained from P. J. Brown’s remarks on the matter, when his exponent of structured programming, Professor Primple remarks, "My program to analyse English sentences works well, but there is a small restriction that all sentences must contain ten words and each word must be of five letters."

The stuff I have written so far starts out with these declarations:–

CONST longeststring = 256; {Can be more, or less. } longestname = 8; {Length of stringnames. TYPE

stringname = PACKED ARRAY [1..longestname] OF CHAR; stringlength = 0..longeststring; stringcontents = PACKED ARRAY 1..longeststring | OF CHAR;

stringitem = RECORD name : stringname; length : stringlength; contents : stringcontents; next : “stringitem END;

stringpointer = “stringitem

In most versions of Pascal, "“stringpointer" would have been declared before "stringitem", and "next" would be of type stringpointer. The Hisoft version won’t let you use the slight forward declaration involved, but this is not a handicap, as it is easily avoided, as shown. Anyway, the declarations above show the sort of data structure I am trying to use in my string handling routines. Whenever a new string is needed, the program includes a NEW(soandso), where the "soandso" is the name of a pointer. Space is then allocated by the run time routines for another record of the type shown above. It may prove to be unnecessary to write the system after all, since an Apple owner I know has suggested that the UCSD string handling routines might work. I’ll let you know if they do... And now a rest, while I try to beat my score of 232 at Adventure. How DO you get past the Plover Room, without falling down a pit?


This is an OCR’d version of the scanned page and likely contains recognition errors.











Page 10 of 51