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PhenixRising
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Joined: 07/11/2023
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Posted: 09:19am 11 Mar 2024

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Manual:

Quote
The other logical operations result in the integer 0 (zero) for false and 1 for true

But:

Print inv 1

The result is -2

Print inv -1

The result is 0

thwill

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Joined: 16/09/2019
Location: United Kingdom
Posts: 4395

Posted: 09:31am 11 Mar 2024

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I'm braced to be told that I am talking out of my arse but INV isn't a logical operation (you might be looking for NOT), it's a bit operation.

> ? Bin$(1, 64)
0000000000000000000000000000000000000000000000000000000000000001
> ? &b1111111111111111111111111111111111111111111111111111111111111110
-2
> ? Bin$(-1, 64)
1111111111111111111111111111111111111111111111111111111111111111
> ? &b0000000000000000000000000000000000000000000000000000000000000000
0

Best wishes,

Tom

MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures

PhenixRising
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Posted: 09:54am 11 Mar 2024

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thwill said I'm braced to be told that I am talking out of my arse but INV isn't a logical operation (you might be looking for NOT), it's a bit operation.

Best wishes,

Tom

Thanks Tom. I do use NOT but I tested INV without consulting the manual

robert.rozee
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Posted: 10:24am 11 Mar 2024

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from page 27 of the User Manual, MMBasic Ver 5.08.00, Revision 4:

Quote NOT INV
invert the logical value on the right (e.g. NOT a=b is a<>b) or bitwise inversion of the value on the right (e.g. a = INV b)

what is interesting is that the above example from the user manual "NOT a=b is a<>b" is wrong:

>
> a=5
> b=6
> ? a<>b
1
> ? not a=b ' interpreted as (not a)=b
0
> ? not (a=b) ' interpreted correctly with brackets
1
>

the priority of both NOT and INV are higher than that of = and <>. this is a good example of why unary operators (which are really just a sub-class of functions) should always have their parameter enclosed in brackets to prevent confusion!

now, as for functions, they present an extra level of mayhem:

>
> sin=12
> ? sin 34
12 34
> ? sin(34)
0.5290826861
>

clearly the mmbasic interpreter is expecting the function's parameter to be enclosed in brackets, but behaves badly if none are present. questions - should it be legal to have a variable with the same name as a function? should it be made mandatory to enclose the parameter lists for functions and unary operators in brackets?

cheers,
rob :-)

JohnS
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Joined: 18/11/2011
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Posted: 10:50am 11 Mar 2024

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If it's meant to be as if
not (a=b)
then the manual could do with a fix - good find if so.

John

robert.rozee
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Posted: 11:06am 11 Mar 2024

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hi John,
i think in the first instance it is an error in the manual, although one that illustrates a classic programming mistake.

a further test:

>
> x=sin 34
Error: Expression syntax
>
> x=sin (34)
> ? x
0.5290826861
>

reveals brackets around function parameters are already mandatory, and that the error here is in allowing function names to be used as variable names. so something like ? sin should give a syntax error, as should sin=1.

the question of how to handle unary operators remains open; i suspect the failure goes way back to when BASIC was first created some 60 years ago. personally, i'd like to see INV, NOT, and - (the last being negation) required to have mandatory brackets around the parameter.

cheers,
rob :-)
Edited 2024-03-11 21:07 by robert.rozee

twofingers

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Posted: 11:28am 11 Mar 2024

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robert.rozee said ... the question of how to handle unary operators remains open; i suspect the failure goes way back to when BASIC was first created some 60 years ago. personally, i'd like to see INV, NOT, and - (the last being negation) required to have mandatory brackets around the parameter. [...]

I don't see the problem.
The MMbasic manual says on page 45:

Quote ... For normal use of NOT or INV the expression to be operated on should be placed in brackets. Eg:
IF NOT (A = 3 OR A = 8) THEN ...

Regards
Michael

‚My name is Ozymandias, king of kings
Look on my works, ye Mighty, and despair!‘
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare
The lone and ...

Geoffg

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Posted: 01:04pm 11 Mar 2024

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robert.rozee said the above example from the user manual "NOT a=b is a<>b" is wrong

Well spotted, thanks Rob.

robert.rozee said unary operators ... should always have their parameter enclosed in brackets to prevent confusion!

NOT does not need to be followed by brackets (for example, NOT PIN(xx)) and Microsoft (in their wisdom) did not require brackets. I understand your point but doing ast you say would cause greater problems.

robert.rozee said should it be legal to have a variable with the same name as a function?

It is not legal for variables to use a function name. The fault is that MMBasic does not have a sufficiently sophisticated error detecting mechanism to detect this... it just stumbles on as best as it can.

Geoff

Geoff Graham - http://geoffg.net

stanleyella

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Joined: 25/06/2022
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Posted: 02:00pm 11 Mar 2024

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this toggles fno 1 or 0.
inc fnc: if fnc=5 then fnc=0:fno=not fno 'in wisdom no endif needed

if fno=0 then
else
Edited 2024-03-12 01:45 by stanleyella

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