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Super BASIC coding style for Minerva
Posted: Sun Feb 26, 2017 3:56 pm
by tcat
Hi,
I have just started exploring `Minerva' system. I was surprised that some pieces of my Super BASIC code need a bit of altering to run.
Program gets sometimes exited from procedures, rather then returning to the caller.
This example will never print "done", when running from the `main' procedure.
The remedy seems to place explicit return statement on line 120.
Code: Select all
100 DEFine PROCedure try
110 IF 1 THEN
120 PRINT "was here 1"
130 ELSE IF 1 THEN
140 PRINT "was here 2"
150 ELSE
160 PRINT "was not here"
170 END IF
180 END DEFine try
190 :
200 DEFine PROCedure main
210 try
220 PRINT "done"
230 END DEFine main
240 :
250 REMark END
What are the general tips for Minerva coding style?
Many thanks
Tomas
Re: Super BASIC coding style for Minerva
Posted: Sun Feb 26, 2017 4:30 pm
by janbredenbeek
tcat wrote:Hi,
I have just started exploring `Minerva' system. I was surprised that some pieces of my Super BASIC code need a bit of altering to run.
Program gets sometimes exited from procedures, rather then returning to the caller.
This example will never print "done", when running from the `main' procedure.
The remedy seems to place explicit return statement on line 120.
Code: Select all
100 DEFine PROCedure try
110 IF 1 THEN
120 PRINT "was here 1"
130 ELSE IF 1 THEN
140 PRINT "was here 2"
150 ELSE
160 PRINT "was not here"
170 END IF
180 END DEFine try
190 :
200 DEFine PROCedure main
210 try
220 PRINT "done"
230 END DEFine main
240 :
250 REMark END
Your IF clauses are not matched by END IFs. The correct syntax is:
Code: Select all
IF condition THEN statement1 [:ELSE statement2]
or
Code: Select all
IF condition THEN
statement1
ELSE
statement2
END IF
In other words: if the statement after THEN is on the same line then it's an inline clause and you don't need END IF, if it's not on the same line you need to end your IF clause with an END IF.
Jan.
Re: Super BASIC coding style for Minerva
Posted: Sun Feb 26, 2017 6:14 pm
by tcat
Hi Jan,
Ah, unbalanced `END-IF(s)'.
Minerva is less forgiving than other ROMs where the `1st END-IF' seems to terminate them all.
Perhaps I am being silly, but is there a better way to format the code without need of deep indents in nesting?
(In cases where SELect ON's cannot be used)
Code: Select all
100 DEFine PROCedure try_if_else
110 IF 1 THEN
120 PRINT 1
130 ELSE IF 2 THEN
140 PRINT 2
150 ELSE IF 3 THEN
160 PRINT 3
170 ELSE IF 4 THEN
180 PRINT 4
190 ELSE IF 5 THEN
200 PRINT 5
210 ELSE IF 6 THEN
220 PRINT 6
230 ELSE IF 7 THEN
240 PRINT 7
250 ELSE IF 7 THEN
260 PRINT 8
270 ELSE IF 8 THEN
280 PRINT 8
290 ELSE IF 9 THEN
300 PRINT 9
310 ELSE
320 PRINT 10
330 END IF : REMark END IF:END IF:END IF:END IF:END IF:END IF:END IF:END IF
340 END DEFine try_if_else
Tomas
Re: Super BASIC coding style for Minerva
Posted: Sun Feb 26, 2017 6:25 pm
by Outsoft
Thanks to help Tomas on it dears
Re: Super BASIC coding style for Minerva
Posted: Sun Feb 26, 2017 6:58 pm
by RWAP
Of course, if it was such a simple example, SELECT on would be much easier to write for the multiple IF statements...
Turbo would also probably report issues with the IF statements if you tried to compile it without all of the matching END IF statements...
Re: Super BASIC coding style for Minerva
Posted: Sun Feb 26, 2017 7:34 pm
by dilwyn
tcat wrote:Hi Jan,
Ah, unbalanced `END-IF(s)'.
Minerva is less forgiving than other ROMs where the `1st END-IF' seems to terminate them all.
Perhaps I am being silly, but is there a better way to format the code without need of deep indents in nesting?
(In cases where SELect ON's cannot be used)
"Less Forgiving" is probably the wrong way of describing this, the older ROMs were a nightmare for not being rigid enough with these, sometime meaning a program would only run on one ROM system. This is one perfect example of why so many older programs seem to fail on modern systems, the older ROMs let you get away with murder.
Deep indents in nesting might look ungainly, but at least you can see where the nesting goes wrong. Each stage here has a one space indent and by the time you get to line 338 at least you can see where the nesting goes wrong. Admittedly, the big indents and nesting look ungainly and horrible, but at least you can see what's going on.
A while back I was trying to convert a program written in an old M$ BASIC with multiple nested single line IF THEN ELSE. Absolute nightmare to debug - I ended up doing just this in order to be able to follow what was (supposed to be) going on. As RWAP says, that particular example could have been converted into a SELect structure, but often there is no easier way where the structure and nesting is so complex.
Code: Select all
100 DEFine PROCedure try_if_else
110 IF 1 THEN
120 PRINT 1
130 ELSE
135 IF 2 THEN
140 PRINT 2
150 ELSE
155 IF 3 THEN
160 PRINT 3
170 ELSE
175 IF 4 THEN
180 PRINT 4
190 ELSE
195 IF 5 THEN
200 PRINT 5
210 ELSE
215 IF 6 THEN
220 PRINT 6
230 ELSE
235 IF 7 THEN
240 PRINT 7
250 ELSE
255 IF 7 THEN
260 PRINT 8
270 ELSE
275 IF 8 THEN
280 PRINT 8
290 ELSE
295 IF 9 THEN
300 PRINT 9
310 ELSE
320 PRINT 10
330 END IF
331 END IF
332 END IF
333 END IF
334 END IF
335 END IF
336 END IF
337 END IF
338 END IF
340 END DEFine try_if_else
Re: Super BASIC coding style for Minerva
Posted: Sun Feb 26, 2017 9:03 pm
by swensont
There is old joke about the headline "man eating tiger". It is a man eating a tiger, or a tiger that eats a man.
Despite what code will run, it is best to wrote code that is clear about that is intended. Adding the right "END IF's" can be critical and should be done for clarity. Intending is also a way of showing intent by having lines at the same level have the same indent.
Tim
Re: Super BASIC coding style for Minerva
Posted: Mon Feb 27, 2017 8:26 am
by tcat
Hi,
As it seems, current Turbo version only gives warnings about obvious `IF-ELSE' termination.
EDIT that I am glad for.
- `IF-ELSE' obvious termination
- if-else_turbo_report.png (8.96 KiB) Viewed 4719 times
Tomas
Re: Super BASIC coding style for Minerva
Posted: Mon Feb 27, 2017 7:23 pm
by ql_freak
The problem with SuperBASIC is, that it doesn't have an "ELSE IF" (compound) statement, like other languages (e. g. C), but just an ELSE. So you normally should write it so:
Code: Select all
IF a$="first"
PRINT 1
ELSE
IF a$="second"
PRINT 2
ELSE
PRINT -1
END IF
END IF
REMark Above is explicit form, you may abbreviate it to:
IF a$="first":REMark 1st IF
PRINT 1
ELSE IF a$="second":REMark 2nd IF
PRINT 2
ELSE
PRINT -1
END IF: END IF:REMark END IFs must match the no of IFs above
This is indeed a shortage of SuperBASIC, I don't know if this (ELSE IF compound statement) was added for SBASIC.
Well, if one isn't afraid of using GOTO (there is a good reason why even modern languages like C++, Java C# have it!), one could use:
Code: Select all
100 IF a$="first"
110 PRINT 1:GO TO 1000:END IF
120 IF a$="second"
130 PRINT 2:GO TO 1000:END IF
140 REMark Add other clauses before line 999
999 PRINT -1
1000
Such a use of GO TO (all go to the same line number) is IMO acceptable, because of the shortage of SuperBASIC. In C (Java, C#) you need a GOTO, if you want jump out of a nested loop to an outer loop, which isn't required (NOT ACCEPTABLE) in SuperBASIC, as all loops have a name and you can use "EXIT loopname".
On Minerva (and afaik with Turbo) there is often a better solution (afaik): You can use SELect ON with integer and string variables, unfortunately this is not possible with SBASIC.
Re: Super BASIC coding style for Minerva
Posted: Tue Feb 28, 2017 7:48 am
by XorA
Code: Select all
Such a use of GO TO (all go to the same line number) is IMO acceptable, because of the shortage of SuperBASIC. In C (Java, C#) you need a GOTO, if you want jump out of a nested loop to an outer loop, which isn't required (NOT ACCEPTABLE) in SuperBASIC, as all loops have a name and you can use "EXIT loopname".
You don't in C you know
https://www.tutorialspoint.com/cprogram ... tement.htm