Simple toggle trick

[Randy Walker]

Long time ago I cane across the need to toggle a variable off and on. Until recently I forgot about this trick. This little snippet demonstrates how the tilde (not) symbol can be used to toggle a variable on each pass.
Run with or without Debugger:

Code: Select all

Repeat
  Select MessageRequester("See toggle Work?", Str(t)+" <<Yes to toggle this value.", #MB_YESNO)
    Case #IDYES
      t = ~ t
    Case #IDNO
      Break
  EndSelect
  Debug t
ForEver
End

[Bisonte]

If this is supposed to be a tip, and it is found by a beginner...
they will be confused at first.

What are these constants?

Please use PureBasic constants and not API constants (which, to my knowledge, only exist in Windows),
even if they are quicker to write... Not everyone use your environment and write in your style.

Thank you.

in this case

Code: Select all

#PB_MessageRequester_YesNo
#PB_MessageRequester_Yes
#PB_MessageRequester_No

[AZJIO]

Code: Select all

t = Bool(Not t)

If you read the flag from the ini file and someone writes 15 there, your version will stop working

[BarryG]

I've always used "t=1-t" because it makes it clear to anyone what it does.

[minimy]

l= 1
l!1
Debug l
l!1
Debug l
This work too

[Piero]

Code: Select all

a=6
a!4
Debug a
a!4
Debug a
a!4
Debug a

Code: Select all

a=~4
Debug 4&a|2
a=~a
Debug 4&a|2
a=~a
Debug 4&a|2

viewtopic.php?p=635000#p635000

[Randy Walker]

Indeed.... more good tricks. Thanks everyone for your contributions!!

[Randy Walker]

If this is supposed to be a tip, and it is found by a beginner...
they will be confused at first.

What are these constants?

Please use PureBasic constants and not API constants
Thank you.

Wow!! Didn't think it would offend anyone. Have it your way...

Code: Select all

Repeat
  Select MessageRequester("See toggle Work?", Str(t)+" <<Yes to toggle this value.", #PB_MessageRequester_YesNo)
    Case #PB_MessageRequester_Yes
      t = ~ t
    Case #PB_MessageRequester_No
      Break
  EndSelect
  Debug t
ForEver
End

[Bisonte]

If this is supposed to be a tip, and it is found by a beginner...
they will be confused at first.

What are these constants?

Please use PureBasic constants and not API constants
Thank you.

Wow!! Didn't think it would offend anyone. Have it your way...
...

Sorry its no offend... But your codes often have some mystical things (for beginners), their are
not in the PB Help ...

[Randy Walker]

Wow!! Didn't think it would offend anyone. Have it your way...
...

Sorry its no offend... But your codes often have some mystical things (for beginners), their are
not in the PB Help ...
[/quote]
Yes, my posts are intended mostly for beginners. I know I'm not going to teach any seasoned users here anything.

[SMaag]

Hi Randy, your code is a good example for don't do that!

Never try to toggle ON/OFF with the binary not! Always use Bool Not.
This is a big differernce.
The binary Not toggles all bits.
The bool Not toggles between #False and #True.

I modified your code to show the Problem.
If I set first t=#True (= 1) and use binary Not, It toggles between 1 and -2 what both is #True.
So you do not get ON/OFF!

Code: Select all

t= #True
Repeat
  Select MessageRequester("See toggle Work?", Str(t)+" <<Yes to toggle this value.", #MB_YESNO)
    Case #IDYES
      t = ~ t
    Case #IDNO
      Break
  EndSelect
  Debug Bool(t)
ForEver
End

if you want to toggle a Bool just do a 0 check!

Code: Select all

Macro ToggleBool(_val_)
 Bool(_val_=0)
EndMacro

t = 1234
Debug Str(t) + " : " + Bool(t)
Debug ""
For I = 1 To 10
  t = ToggleBool(t)
  Debug t
Next

[Randy Walker]

Hi Randy, your code is a good example for don't do that!

Great!! Thanks for pointing that out. Makes my Original post even more worth while.

[minimy]

One way more

Code: Select all

a= 1
Debug a
a= Abs(a-1)
Debug a
a= Abs(a-1)
Debug a

[mk-soft]

Is not better because ABS first converts everything into double and then back again

[mk-soft]

Short way for ASM and C backend

Code: Select all

Macro Toggle(x)
  x=~x&1
EndMacro

a=#True
Toggle(a)
Debug a
Toggle(a)
Debug a
Toggle(a)
Debug a