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Forum Index : Microcontroller and PC projects : True/False conflict using INV?
| Author | Message | ||||
| PhenixRising Guru  Joined: 07/11/2023 Location: United KingdomPosts: 858 |
Manual: But: Print inv 1 The result is -2 Print inv -1 The result is 0 |
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thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4038 |
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 Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 858 |
Thanks Tom. I do use NOT but I tested INV without consulting the manual  |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2350 |
from page 27 of the User Manual, MMBasic Ver 5.08.00, Revision 4: 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 :-) |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3801 |
If it's meant to be as if not (a=b) then the manual could do with a fix - good find if so. John |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2350 |
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 |
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| twofingers Guru Joined: 02/06/2014 Location: GermanyPosts: 1241 |
I don't see the problem. The MMbasic manual says on page 45: Regards Michael causality ≠ correlation ≠ coincidence |
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Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3194 |
Well spotted, thanks Rob. 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. 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 |
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stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2127 |
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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