Amiga Computing - Commodore Is Awesome

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allionew p mag of t h e t o p t e l l y s h o w •IDG D I A 1 9 771355 173022 1 i AJ III be bock on pose 16 of this rather splendid mog. See the review of True ties on video. Be amazed ot the quality of the words and, in fad, the pictures too! Six times i n Videos! Freddy Krueger's jacket! Shawshank Redemption and Andre gear! And loads more! INSIDE: MOV's Very own Oscar winners for last year, How to make a blockbusting movie, interview with Kryten (Red Dwarf) and Dennis Hopper (Speed 1
vs I) • • 0 • • • • • • • • • 111 • his months theme, in a nutsnell, is about writing understandable code, and while most programmers will doubtless have their own ideas on what constitutes an easy-to-read program, I thought it might be useful to recap on the Conventions I use. One thing that is obviously helpful is the use of understandable names for variables and I tend to use lowercase names. adding underscore characters to improve readability. For example, an Mexx statement which reads: iii t_f ligT f. se t nit fle e - didif lUE .1 /, has decided to dolt *I !s s I n With m function names I capitalise the first letter of each y part of the function name - CalculateAverageo, m GetResponsen and so on. ARexx i itself doesn't care about the capitalisation (function n names are all treated as upper case anyway) d but the above mentioned arrangement does , seem to aid readabefity. m Above all make sure the name tells you something u about what the function does -;t may c seem all very clever at the time to create a function h called HaveANiceDay() but six months later p its likely to be you who's sitting there wondering r what on earth It does! e ARexx variables are effectively typeless so you f don't need to declare variables as hokdino enumbers, strings and so on Despite this, rbelieve it is actually very useful to be able to r imply something about the type of data held in ea variable from its name. d You may have noticed that I often add a S t Suffix to Men variables which are specifically o used to hold text smngs. I might, for example suse nameS and address$ to collect name and o address strings from a user. If. on the other m hand. I knew that the user input was going to e be a number then id use variable names like t value, age, x, or n. h should point out that in this case these i 'pseudo type' arrangements are not a common n ARexx convention and internally. ARexx cares g little about the types of values placed into a l variable. Nevertheless the convention has i Served me well and it is one I recommend. k e With some advanced applications it is also : occasionally useful to adopt additional conventions. Prefixing global variables with the character g_ and suffixing pointer variables I1a5511 wding• •••• Il • ••• lte115 ••• ••• i[H 1 Praire.. 1 1 •: -J1 ite rkbe nch - 1 , 1 dmi ;She ti * spy his micro w t ▪ Fine tC e 1 1 0 sut s lions •e sotts H • •d :C ld:t. tc4 s t t * / Set pe rsm•te rs to be to rotor units. .0 . ' tit 0o Outer simply by loading values into vanables [which are subsequently never changed[ My preference is to use uppercase names for constant values like this. ESCAPE • 'WA By getting into the habit of placing such Fair comment All Mem( programs have to start with a comment line so there's a good chance there will, at least, be a program name at the start of your scripts. But why stop there - additional comments can make a world of difference to understanding a program. Don't make the mistake. inCidentally, of thinking that comments are just for the benefit of other users and that you understand your code well enough not to need additional remarks. You may understand your code when you write it. but it amazing how code tricks, which seemed perfectly obvious at the time they were written, appear to loose their 'inherent obviousness' as time goes on. You should not get carried away to the point where you impose unreasonable numbers of restrictions on either yourself or anyone else who has to read your code. The aim is to adopt a set of coding guidelines which help and are easily usable, and luckily, for the most part at least, all that s needed is common-sense coupled to a consistent methodical approach! Copy Je st T O N . ▪ ftine lt 1 1 1 1 t • C a C i s g::1 : h e• a / d • Oft the So 4. I t thpfe •F /4. " •.4 t .rne .141 - , b r pleti o " - • a/NOV a ' r t e . 0/ A hills extra Cara g when wrelona Allema script* can produce clividanda ) In the ions run! : t Using _p can help tell e you something about the definitions near the start of a program. you will data stored in the variable. l t Another rule of thumb' i concerns avoiding always know where to look for them the separation also makes the values easy to change the use of absolute Constants n within the bulk of and because symbolic names rather than the your program code unfortunately. ARexx underlying definitions themselves are used, the doesn t provide much direct help in this area program automatically becomes easier to but 'pseudo constant' values can still be set up understand. This 'trick' is especially useful when dealing with control character sequences (this of course was what last months instalment was all about' but the ideas can also be applied in other areas as well. There is. for instance. a good case, particularly with larger scripts, for eliminating explicit text messages from the bulk of your code. If. for example, you Set up this initial error message definition Indium/ . 'sorry this •ILUS is not correct' then within the main sections of the program the appropnate error message can be displayed using: say WRONG_ViLin Equally important is trie fact mat the message. which may actually get used in a number of different code areas of the script, is now defined in a single place This ensures that any changes Co the initial definition results in those modifications automatically being used throughout the program! <strong>Amiga</strong> <strong>Computing</strong> MAY 1995 •••• • If qou haue trouble understanding Ahem (Ode qou'ue written months or gears ago, the5e guide lines from Paul OLIPrad (fluid make tour coding life ea5ier
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