Elegant Logic test

[Mike Trader]

Is there an elegant way to code this:

LOCAL a,b,c AS LONG ' for example

IF a OR b OR c THEN        ' If one is present then 
  IF a AND b AND c THEN  ' all must be present  
    ' Want the Else
  ELSE
    MissingFlag = 1 ' Error, one or more is missing
  END IF
END IF

[Don Schullian]

IF (A*B*C) = 0 THEN
? "Something's missing!"
END IF

[Paul Dixon]

Mike,
the outer IF THEN.. ENDIF loop is redundant. Just use:

  IF a AND b AND c THEN  ' all must be present  
    ' Want the Else
  ELSE
    MissingFlag = 1 ' Error, one or more is missing
  END IF

It will do the same job since if all of a,b and c are present then at least one of them must be.

Paul.

[David Roberts]

If there is any knowledge on the probability of being false then with a descending sort with 'a' as the most likely to be false and so on then we could use

If a Then
  If b Then
    If c Then
      Exit If
    Else
      MissingFlag = 1
    End If
  Else
    MissingFlag = 1
  End If
Else
  MissingFlag = 1
End If

BTW Mike your code fails if all are missing but not so, obviously, when the outer loop is removed as Paul suggested.

[Michael Mattias]

I think this might actually be a real case for using the IMP operator. (which I have never been able to find a case for).

No, I haven't had enough coffee yet to do this, but it just might work AND score quite high in the 'panache points' area.

[Michael Mattias]

Forget IMP.

IF (A OR B OR C) AND (A AND B AND C) THEN
  If one is true then all are true
ELSE
  ???
END IF

[code]
No, that's not right is it? He wants the flag set ONLY if one is true but not all (i.e., flag not set if all false).

IMP might be back on the table after all. (sure you could do it with an ELSEIF ( A OR B OR C alone) above, but there's no style points available for that).

[John Gleason]

How about six ticks worth:

#COMPILE EXE
#DIM ALL

FUNCTION PBMAIN () AS LONG
    LOCAL a,b,c AS LONG
    a = 1:b = 1:c = 1
'   a = 0:b = 1:c = 1 'zero any of three out and it results in 0 (not ok)
     a = a AND b      'These 3 lines are just 6 ticks to do logic
     a = a AND c      '                 "
     IF a THEN        '                 "
'    IF a AND b AND c THEN << Tried this, but... let's just say more than 6 ticks ;o)
'    You don't need the initial OR logic since that will be determined by the AND logic
        ? "ok"
     ELSE
        ? "not ok"
     END IF
     
END FUNCTION

[John Gleason]

Oops, got it to 5 ticks:

#COMPILE EXE
#DIM ALL

FUNCTION PBMAIN () AS LONG
    LOCAL a,b,c AS LONG
    a = 1:b = 1:c = 1
'   a = 0:b = 1:c = 1 'zero any of three out and it results in 0 (not ok)
'   IF a AND b AND c THEN   '<< Tried this, but... just say more than 6 ticks ;)
    IF (a AND b AND c) THEN '<< Tried this--force to bit logic--and lo and behold, 5 ticks!
'    You don't need the initial OR logic since that will be determined by the AND logic
        ? "ok"
     ELSE
        ? "not ok"
     END IF
     
END FUNCTION

[Walt Thompson]

Hi Mike;

Perhaps the XOR function will work.

LOCAL a,b,c AS LONG ' for example

IF a OR b OR c THEN ' If one is present then
IF a AND b AND c THEN ' all must be present
' Want the Else
ELSE ' Error, one or more is missing
IF a XOR b THEN MissingFlag = 1 : EXIT IF
IF a XOR c THEN MissingFlag = 1 : EXIT IF
IF b XOR c THEN MissingFlag = 1 : EXIT IF

END IF
END IF

[John Harvill]

 
LOCAL a,b,c AS LONG ' for example
 
IF a AND b AND c THEN ' all must be present
   ' Do something
ELSEIF  a OR b OR c  THEN ' at least one is present
   MissingFlag = 1 'Error, one or two is missing
ELSE
   'Optional -- all are missing
END IF

Sincerely,
John Harvill

[John Gleason]

I just read the previous posts (yes, being in the fog of... fog) and saw Paul already did "a AND b AND c", but I had checked that and it was like 9 ticks, so I thought, "5 is less than 9", case closed. Um, nope. "a AND b AND c" will "short circuit" similar to like what Dave's code above does but with no knowledge necessary of a, b, or c. Hence, it will average 4.5 ticks, and correct me if I'm wrong, but 4.5 is less than 5. My code will beat Paul's code--yeah, sure, that's gonna happen. Cold fusion COULD become reality by 2009 too.

[Rodney Hicks]

Or maybe this

#COMPILE EXE
#DIM ALL
#INCLUDE "Win32API.inc"
FUNCTION PBMAIN () AS LONG
  LOCAL a,b,c AS LONG ' for example
  LOCAL MissingFlag AS LONG
  a=1:b=1:c=0
'  IF a OR b OR c THEN ' If one is present then
'    IF a AND b AND c THEN ' all must be present
'     Want the Else
'    ELSE ' Error, one or more is missing
IF (a XOR b) OR (b XOR c) THEN MissingFlag = 1:MSGBOX "MissingFlag="+FORMAT$(MissingFlag),%MB_TASKMODAL
'    END IF
'  END IF
END FUNCTION

Or, more clearly

#COMPILE EXE
#DIM ALL
#INCLUDE "Win32API.inc"
FUNCTION PBMAIN () AS LONG
  LOCAL a,b,c AS LONG ' for example
  LOCAL MissingFlag AS LONG
  a=0:b=0:c=1       'the if statement is ignored if all are equal to 1 or 0
  IF (a XOR b) OR (b XOR c) THEN MissingFlag = 1:MSGBOX "MissingFlag="+FORMAT$(MissingFlag),%MB_TASKMODAL
END FUNCTION

[Mike Trader]

Wow, you guys are so creative!
I should have defined elegant a little better... meaning a one line solution so:

IF (a XOR b) OR (b XOR c) THEN ? "Error"

IF (a*b*c) = 0 THEN ? "Error"
Look good. Unfortunatly the logic of (a*b*c) is not correct

Speed was not an issue cos I thought logic would do it, but since the variables are actually DWORDs values (holding the number of bytes) and I didn't consider using multiplication speed now becomes interesting.
So you are right, a speed test is in order.

Using timing Macro's developed with the kind help of Michael W on the MASM site:
http://www.masm32.com/board/index.php?board=30.0



On my P4 Win XP Pro box I get:
424
188
336

The DWORD multiplication is the fastest, the problem is the logic fails... Darn.

[Michael Mattias]

>but since the variables are actually DWORDs values (holding the number of bytes)...

Then you can't use AND unless you use ISTRUE.

e.g, ( 2 AND 4) is false, but (ISTRUE(2) and ISTRUE(4)) is true.

MCM

[John Gleason]

Mike, check out your original post, the code from which is included below, then insert the code into your timing program and run all three example timings. 7 ticks is the max I got!

    '=======================
    ErrorFlag = 0
    COUNTER_BEGIN(nLoops, %HIGH_PRIORITY_CLASS)
      IF a OR b OR c THEN
         IF a AND b AND c THEN
         ELSE
'         ErrorFlag = 1   ' Do not time this
         END IF
      END IF
    COUNTER_END
      IF a OR b OR c THEN
         IF a AND b AND c THEN
         ELSE
            ErrorFlag = 1
         END IF
      END IF
    s = s + "3: ErrorFlag=" + STR$(ErrorFlag) + ",  Clks="+STR$(CounterCycles) + $CRLF
    '=======================

[Greg Turgeon]

Speed? Yeah.

'============
MACRO AllOrNone(a,b,c,errorFlag)
'-- errorFlag returns zero/nonzero (not 0/1 or 0/-1)
MACROTEMP Done
!  xor   eax,        eax

!  mov   ebx,        a
!  mov   ecx,        b
!  mov   edx,        c

!  test  ebx,        ebx
!  setnz al

!  test  ecx,        ecx
!  setnz cl

!  test  edx,        edx
!  setnz dl

!  add   al,         cl
!  add   al,         dl

!  test  eax,        eax
!  jz    Done
!  sub   eax,        &b11
Done:
!  mov   errorFlag,  eax
END MACRO

Revised later for minor tightening (and because I couldn't get to sleep ).

[John Harvill]

Given that A, B, and C represent the quantity of something, and the goal is to determine whether one or two variables have a quantity of zero, then:

IF ROUND( 0.66 * CSNG( SGN( A ) + SNG( B ) + SNG( C ) ), 0 ) = 1 THEN MissingFlag = 1 ' Error, one or two is missing

Sincerely,
John Harvill

[Claudio DalZovo]

"If one is true all must be true" can be said as "if one is true" implies "all must be true) ... so:

if not((a+b+c) imp (a*b*c)) then missingflag=1

Just to use imp ... I think the original code is much more clear.

However, as already stated previously, this doesn't works because imp works on left and right part of expressions bitwise and result is dependent from true values of a,b,c.
Should be

if not(istrue(a+b+c) imp istrue(a*b*c)) then missingflag=1

but it's going to be too complex ...

[John Tate]

Here is my one liner.

#COMPILE EXE
#DIM ALL

FUNCTION PBMAIN () AS LONG

LOCAL a,b,c,flag,var1,var2 AS LONG
a = 1:b = 0 :c = 1
IF (ISFALSE(a)OR ISFALSE(b) OR ISFALSE(c)) THEN MSGBOX "all or one is missing" ELSE MSGBOX "all are present"
END FUNCTION

John Tate