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Active Forums => QB64 Discussion => Topic started by: xra7en on June 07, 2019, 06:08:20 pm

Title: REALLY old basic code question
Post by: xra7en on June 07, 2019, 06:08:20 pm

From 1971 - what does this mean?

Code: QB64: [Select]

if x > 400 then .2343

is this the same as

Code: QB64: [Select]

if x > 400 then x = .2343

??

Thanks

Title: Re: REALLY old basic code question
Post by: RhoSigma on June 07, 2019, 06:48:57 pm

The .2343 is probably a label to jump to. I think i remember that leading dots were used to denote labels (it's still used todays in assembly for local labels for instance).

The IF THEN statement makes a GOTO if it recognizes a label, today we would need to write IF xxx GOTO label instead.

That's my best guess, maybe somebody of the older fellows here on the forum can confirm or dismiss it for sure.

Title: Re: REALLY old basic code question
Post by: xra7en on June 07, 2019, 06:55:29 pm

that be it. I looks through the spaghetti code and found the line number, and it matched the flow!
thanks!

Title: Re: REALLY old basic code question
Post by: TempodiBasic on June 07, 2019, 08:11:19 pm

Hi xra7en
IMHO in my little experience of very old code

Quote

IF condition THEN NumberOfLine/Label

It's new for me the use of a point as starter of the name of the label, but it is possible to make a similar name label in QB Qbasic and QB64, I have tested it. And RhoSigma is smarter than me!

Title: Re: REALLY old basic code question
Post by: xra7en on June 08, 2019, 12:45:21 pm

well one thing it might be is a smudge. it is an old copy I found in my days of xeroxing pages from the library(eons ago when I had my TIMEX SINCLAIR hehe). It could just be a "dot" as in smudge too LOL - it's from an old tandy book LOL thats all I remember

Title: Re: REALLY old basic code question
Post by: xra7en on June 08, 2019, 12:49:40 pm

two others I ran across were

Code: QB64: [Select]

A=B=C=D=F=0

I assume that makes ALL those vars = 0?

and this one is a stumper

Code: QB64: [Select]

CHANGE M$ M(I) ' or something to that effect

Title: Re: REALLY old basic code question
Post by: TempodiBasic on June 09, 2019, 06:02:36 am

About
Multiple assignations and initializations in one row
A=B=C=D=F=0

I never met any BASIC that do it.
You must split the assignations and initializations

About the other syntax It seems to be convertion from String to Integer
Here info about tour Sinclair
https://it.m.wikipedia.org/wiki/Sinclair_BASIC (https://it.m.wikipedia.org/wiki/Sinclair_BASIC)

Title: Re: REALLY old basic code question
Post by: SMcNeill on June 09, 2019, 06:57:10 am

Quote from: TempodiBasic on June 09, 2019, 06:02:36 am

About
Multiple assignations and initializations in one row
A=B=C=D=F=0

I never met any BASIC that do it.
You must split the assignations and initializations

About the other syntax It seems to be convertion from String to Integer
Here info about tour Sinclair
https://it.m.wikipedia.org/wiki/Sinclair_BASIC (https://it.m.wikipedia.org/wiki/Sinclair_BASIC)

It’s perfectly valid; it’s just not assignments. It’s mathematical calculations. Think of it as:

A = (B = (C = (D = (E = (F = 0)))))

So if F = 0, that innermost result is -1, basically making the calculation: A = (B = (C = (D = (E = -1))))

And, if F <> 0, that innermost result is 0, basically making the calculation: A = (B = (C = (D = (E = 0))))

And it just continues to solve the formula until it ends up giving A a final value of either -1 (TRUE) or 0 (FALSE).

**************************

I’ve seen this type of logic in the past before, and if I remember correctly, it’s basically a quick way to determine if all the values are set, or not. If B, C, D, E, F are all 0, A should be (either 0 or -1, but I’m not certain what the result actually is, without testing it.). If one value is non-zero, the value of A should be reversed.

If the values are anything other than Boolean truth values (0 or -1), I can’t really see such a formula having any meaning at all. I guess more of the code would have to be shared, to try and actually sort out what it’s supposed to do, but it’s basically an assignment structure to determine if A is 0 or -1, in the end.

For easy reference, think of A = B = C. If B = C, then A = -1, otherwise A = 0...

It’s the same principle; just carried out to an extreme level.

In the end, you can think of it as a formula which calculates the value of A from:

E = F = 0
D = E = F
C = D = E
B = C = D
A = B = C

Title: Re: REALLY old basic code question
Post by: TempodiBasic on June 09, 2019, 08:02:01 am

Thanks Steve

I have thought that it was a dialect basic feature!

I try code in our QB64Ide

Code: QB64: [Select]

PRINT A = (B = (C = (D = (E = (F = 0)))))
PRINT A = B = C = D = F = 0
PRINT A
PRINT B
PRINT C
PRINT D
PRINT F
 

it is possible to use either formulas (with and without parenthesis) with no syntax error

I think it is useful in a control statement like IF or SELECT CASE or ON.. GOTO...
here attachment of code
[ This attachment cannot be displayed inline in 'Print Page' view ]

as you can see I am not so able to copy and paste because I have two different output for line 1 and line 2 of code! Sorry

Title: Re: REALLY old basic code question
Post by: xra7en on June 09, 2019, 10:58:53 am

Here are a couple of pics of the code in quesiton (sorry for the quality)

I think this is 1979 TANDY book. I have one coming from amazon.
CHANGE code
https://ibb.co/F8HYVrs

The x = y= z etc..
https://ibb.co/CV4WWJc

That is very interesting with the shortcut just making sure all the vars are zero (check) or all the vars are zero (assign - which is what I thought it was)

Title: Re: REALLY old basic code question
Post by: bplus on June 09, 2019, 11:52:45 am

Ah! Your CHANGE looks like VAL() change a string into a number.

Title: Re: REALLY old basic code question
Post by: xra7en on June 09, 2019, 12:17:22 pm

Quote from: bplus on June 09, 2019, 11:52:45 am

Ah! Your CHANGE looks like VAL() change a string into a number.

hmmm insteresting... I might try that (soon as I run this mosnter LOL) still building it

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