<> Not Equal To != ?

nicholasjames
nicholasjames Junior Member
in NetLinx Studio
Someone asked me why I use "<>" instead of "!=". The Reference states that "<>" is the operator for "Not Equal To" so I've always used that. However some people use "!=", and even some code examples in the Reference uses "!=", and clearly they perform the same function.

However, operator precedence states "!" has the highest precedence of any operator, Level 1, whereas "<>" is down at Level 5. The "=" is also at Level 5, right before "==" and "<>".

Could using one over the other cause logic problems? It could just be unpublished that "!=" is automatically compiled to mean "<>" and thereby always has the same precedence. Perhaps the code in which the precedence of "!" changes the result when combined with "=" is simply un-writable.
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  • rrdbstudios
    rrdbstudios
    nicholasjames wrote: »
    Someone asked me why I use "<>" instead of "!=". The Reference states that "<>" is the operator for "Not Equal To" so I've always used that. However some people use "!=", and even some code examples in the Reference uses "!=", and clearly they perform the same function.

    However, operator precedence states "!" has the highest precedence of any operator, Level 1, whereas "<>" is down at Level 5. The "=" is also at Level 5, right before "==" and "<>".

    Could using one over the other cause logic problems? It could just be unpublished that "!=" is automatically compiled to mean "<>" and thereby always has the same precedence. Perhaps the code in which the precedence of "!" changes the result when combined with "=" is simply un-writable.

    I wish there was a "Like" button for your title..

    I cant speak for if it changes while compiling, but by habbit I use "!=" and have never had any issues.

    My .02
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  • a_riot42
    a_riot42 AMX Wizard
    nicholasjames wrote: »
    Someone asked me why I use "<>" instead of "!=". The Reference states that "<>" is the operator for "Not Equal To" so I've always used that. However some people use "!=", and even some code examples in the Reference uses "!=", and clearly they perform the same function.

    However, operator precedence states "!" has the highest precedence of any operator, Level 1, whereas "<>" is down at Level 5. The "=" is also at Level 5, right before "==" and "<>".

    Could using one over the other cause logic problems? It could just be unpublished that "!=" is automatically compiled to mean "<>" and thereby always has the same precedence. Perhaps the code in which the precedence of "!" changes the result when combined with "=" is simply un-writable.

    Using != burned me once so I stopped using it for not equal to and only use <> now. != actually is different than <>. It means, check if the right side is equivalent to the not of the left side. Usually this works, but not always. Break the habit if you can, to write bug free code.
    Paul
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  • mpullin
    mpullin Obvious Troll Account, Marked for Deletion
    a_riot42 wrote: »
    Using != burned me once so I stopped using it for not equal to and only use <> now. != actually is different than <>. It means, check if the right side is equivalent to the not of the left side. Usually this works, but not always. Break the habit if you can, to write bug free code.
    Paul
    Could we have details please, if the code is possible to share? I'm curious; I use != and never had an issue. I always thought != compiled to not equal and that NetLinx didn't treat the ! as a bitwise op in this context.
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  • a_riot42
    a_riot42 AMX Wizard
    mpullin wrote: »
    Could we have details please, if the code is possible to share? I'm curious; I use != and never had an issue. I always thought != compiled to not equal and that NetLinx didn't treat the ! as a bitwise op in this context.

    I'll see if I can find it, but it was a couple of years ago and my memory is foggy about what the code was. But it was a subtle bug, and took me a while to figure out, so I was pissed that it was caused by what would have worked in almost every other language.
    Paul

    EDIT: This was hashed out some time ago

    http://www.amxforums.com/showthread.php?3631-!-gotcha&highlight=not+equal+to
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  • ericmedley
    ericmedley Senior Member - 3709 Posts
    I too use <> but that's because I'm old and set in my ways :)

    I've ran into issues with != myself too. At the time I just wrote it off to one of those pesky integer 'really' being evaluated as a long for some reasons or other. A lot of times I have to curb my curiosity about why something works or doesn't for getting the job done and over.
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  • a_riot42
    a_riot42 AMX Wizard
    If you write an if guard using != that ends up checking if 0 is not equal to 2, what happens?

    IE:
    integer iZero = 0
integer iTwo = 2

if (iZero != iTwo)
{
  doSomething()
}

    We know 0 is not equal to 2 so this should always evaluate to true and doSomething gets called. But I think what happened in my case was the bang flipped 0 to 1 and then checked to see if 1 = 2 which is false of course, and so it evaluates to false and doSomething doesn't get called like it should. I can't test it at the moment but I seem to recall it was something like this that got me.
    Paul
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  • Auser
    Auser Junior Member
    a_riot42 wrote: »
    Using != burned me once so I stopped using it for not equal to and only use <> now. != actually is different than <>.

    +1. (Plus other stuff to make the message long enough).
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  • vining
    vining X Member
    I'm one of those who seldom use <> and favor != instead and I don't recall ever having any issue using it. As far as precedence goes I can't see how the ! in this case could be considered as a "not" and take that precedence. If it were a not the majority of the tests below wouldn't work since any value over 0 on the left side of the comparison would then equal 0 and if a 0 would it would then equal 1. The left side would become a boolean value 1 or 0 and it doesn't.

    In the below tests I see nothing to make me think that the compiler isn't taking the != combination and translating to <>. The only odd thing this test revealed is when I assigned my two chars.

    STACK_VAR CHAR cChar1;
    STACK_VAR CHAR cChar2;

    cChar1 = '';
    cChar2 = '';

    When I print to diagnostics I get:
    Line 23 (17:30:08):: TEST cChar1-[ @ ] & cChar2-[ @ ] :DEBUG<297>

    Not sure what's up with that but everything else regarding != seems to work just like <> with no odd behavior.


    Line      1 (17:30:08)::  TEST nIntNum1-[ 6 ] == nIntNum2-[ 6 ] :DEBUG<145>
Line      2 (17:30:08)::  TEST nLongNum1-[ 66000 ] == nLongNum2-[ 66000 ] :DEBUG<150>
Line      3 (17:30:08)::  TEST cChar1-[ a ] == cChar2-[ a ] :DEBUG<155>
Line      4 (17:30:08)::  TEST cStr1-[ test ] == cStr2-[ test ] :DEBUG<160>
Line      5 (17:30:08)::  TEST nIntNum1-[ 2 ] != nIntNum2-[ 6 ] :DEBUG<172>
Line      6 (17:30:08)::  TEST nLongNum1-[ 1 ] != nLongNum2-[ 66000 ] :DEBUG<177>
Line      7 (17:30:08)::  TEST cChar1-[ z ] != cChar2-[ a ] :DEBUG<182>
Line      8 (17:30:08)::  TEST cStr1-[ dog ] != cStr2-[ cat ] :DEBUG<187>
Line      9 (17:30:08)::  TEST nIntNum1-[ 0 ] != nIntNum2-[ 10 ] :DEBUG<201>
Line     10 (17:30:08)::  TEST nLongNum1-[ 0 ] != nLongNum2-[ 28800 ] :DEBUG<206>
Line     11 (17:30:08)::  TEST cChar1-[ 0 ] != cChar2-[ 1 ] :DEBUG<211>
Line     12 (17:30:08)::  TEST cStr1-[ 0 ] != cStr2-[ 5 ] :DEBUG<216>
Line     13 (17:30:08)::  TEST nIntNum1-[ 0 ] == nLongNum1-[ 0 ] :DEBUG<232>
Line     14 (17:30:08)::  TEST nLongNum1-[ 10 ] == nIntNum2-[ 10 ] :DEBUG<237>
Line     15 (17:30:08)::  TEST cChar1-[ a ] == cStr1-[ a ] :DEBUG<242>
Line     16 (17:30:08)::  TEST cStr2-[ z ] == cChar2-[ z ] :DEBUG<247>
Line     17 (17:30:08)::  TEST nIntNum1-[ 2 ] != nLongNum1-[ 0 ] :DEBUG<259>
Line     18 (17:30:08)::  TEST nLongNum2-[ 10 ] != nIntNum2-[ 0 ] :DEBUG<264>
Line     19 (17:30:08)::  TEST cChar1-[ c ] == cStr1-[ cat ] :DEBUG<271>
Line     20 (17:30:08)::  TEST cStr2-[ dog ] == cChar2-[ d ] :DEBUG<276>
Line     21 (17:30:08)::  TEST nIntNum1-[ 0 ] == nIntNum2-[ 0 ] :DEBUG<290>
Line     22 (17:30:08)::  TEST nLongNum1-[ 0 ] == nLongNum2-[ 0 ] :DEBUG<295>
Line     23 (17:30:08)::  TEST cChar1-[ @ ] & cChar2-[ @ ] :DEBUG<297>
Line     24 (17:30:08)::  TEST cChar1-[ @ ] == cChar2-[ @ ] :DEBUG<301>
Line     25 (17:30:08)::  TEST cStr1-[  ] == cStr2-[  ] :DEBUG<306>
Line     26 (17:30:08)::  TEST nIntNum1-[ 0 ] != nIntNum2-[ 2 ] :DEBUG<318>
Line     27 (17:30:08)::  TEST nLongNum1-[ 0 ] != nLongNum2-[ 2 ] :DEBUG<323>
Line     28 (17:30:08)::  TEST cChar1-[ a ] != cChar2-[ z ] :DEBUG<328>
Line     29 (17:30:08)::  TEST cStr1-[ z ] != cStr2-[ a ] :DEBUG<333>
Line     30 (17:30:08)::  TEST nIntNum1-[ 0 ] != nIntNum2-[ 1 ] :DEBUG<347>
Line     31 (17:30:08)::  TEST nLongNum1-[ 1 ] != nLongNum2-[ 0 ] :DEBUG<352>
Line     32 (17:30:08)::  TEST cChar1-[ z ] != cChar2-[ t ] :DEBUG<357>
Line     33 (17:30:08)::  TEST cStr1-[ zoo ] != cStr2-[ test ] :DEBUG<362>

    The Code: 
    DEFINE_PROGRAM  

if(nTestRun)
     {
     STACK_VAR INTEGER nIntNum1;
     STACK_VAR INTEGER nIntNum2;
     STACK_VAR LONG nLongNum1;
     STACK_VAR LONG nLongNum2;
     STACK_VAR CHAR cChar1;
     STACK_VAR CHAR cChar2;
     STACK_VAR CHAR cStr1[12];
     STACK_VAR CHAR cStr2[12];
     
     nIntNum1  = 6;
     nIntNum2  = 6;
     nLongNum1 = 66000;
     nLongNum2 = 66000;
     cChar1 = 'a';
     cChar2 = 'a';
     cStr1 = 'test';
     cStr2 = 'test';
     
     if(nIntNum1 != nIntNum2)
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] != nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] == nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(nLongNum1 != nLongNum2)
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] != nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] == nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cChar1 != cChar2)
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] != cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] == cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(cStr1 != cStr2)
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] != cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] == cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     nIntNum1  = 2;
     nIntNum2  = 6;
     nLongNum1 = 1;
     nLongNum2 = 66000;
     cChar1 = 'z';
     cChar2 = 'a';
     cStr1 = 'dog';
     cStr2 = 'cat';
     
     if(nIntNum1 != nIntNum2)
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] != nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] == nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(nLongNum1 != nLongNum2)
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] != nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] == nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cChar1 != cChar2)
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] != cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] == cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(cStr1 != cStr2)
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] != cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] == cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     nIntNum1  = 0;
     nIntNum2  = 10;
     nLongNum1 = 0;
     nLongNum2 = 28800;
     cChar1 = '0';
     cChar2 = '1';
     cStr1 = '0';
     cStr2 = '5';
     
     if(nIntNum1 != nIntNum2)
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] != nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] == nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(nLongNum1 != nLongNum2)
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] != nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] == nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cChar1 != cChar2)
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] != cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] == cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(cStr1 != cStr2)
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] != cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] == cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     nIntNum1  = 0;
     nIntNum2  = 10;
     nLongNum1 = 0;
     nLongNum2 = 10;
     cChar1 = 'a';
     cChar2 = 'z';
     cStr1 = 'a';
     cStr2 = 'z';
     
     if(nIntNum1 != nLongNum1)
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] != nLongNum1-[ ',itoa(nLongNum1),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] == nLongNum1-[ ',itoa(nLongNum1),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(nLongNum2 != nIntNum2)
	  SEND_STRING 0,"'TEST nLongNum2-[ ',itoa(nLongNum2),' ] != nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum2),' ] == nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cChar1 != cStr1)
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] != cStr1-[ ',cStr1,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] == cStr1-[ ',cStr1,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(cStr2 != cChar2)
	  SEND_STRING 0,"'TEST cStr2-[ ',cStr2,' ] != cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cStr2-[ ',cStr2,' ] == cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     nIntNum1  = 2;
     nIntNum2  = 0;
     nLongNum1 = 0;
     nLongNum2 = 10;
     cChar1 = 'c';
     cChar2 = 'd';
     cStr1 = 'cat';
     cStr2 = 'dog';
     
     if(nIntNum1 != nLongNum1)
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] != nLongNum1-[ ',itoa(nLongNum1),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] == nLongNum1-[ ',itoa(nLongNum1),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(nLongNum2 != nIntNum2)
	  SEND_STRING 0,"'TEST nLongNum2-[ ',itoa(nLongNum2),' ] != nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum2),' ] == nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cChar1 != cStr1)
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] != cStr1-[ ',cStr1,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] == cStr1-[ ',cStr1,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(cStr2 != cChar2)
	  SEND_STRING 0,"'TEST cStr2-[ ',cStr2,' ] != cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cStr2-[ ',cStr2,' ] == cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     nIntNum1  = 0;
     nIntNum2  = 0;
     nLongNum1 = 0;
     nLongNum2 = 0;
     cChar1 = '';
     cChar2 = '';
     cStr1 = '';
     cStr2 = '';
     
     if(nIntNum1 != nIntNum2)
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] != nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] == nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(nLongNum1 != nLongNum2)
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] != nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] == nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] & cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
     if(cChar1 != cChar2)
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] != cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] == cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(cStr1 != cStr2)
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] != cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] == cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     nIntNum1  = 0;
     nIntNum2  = 2;
     nLongNum1 = 0;
     nLongNum2 = 2;
     cChar1 = 'a';
     cChar2 = 'z';
     cStr1 = 'z';
     cStr2 = 'a';
     
     if(nIntNum1 != nIntNum2)
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] != nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] == nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(nLongNum1 != nLongNum2)
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] != nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] == nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cChar1 != cChar2)
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] != cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] == cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(cStr1 != cStr2)
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] != cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] == cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     nIntNum1  = 0;
     nIntNum2  = 1;
     nLongNum1 = 1;
     nLongNum2 = 0;
     cChar1 = 'z';
     cChar2 = 't';
     cStr1 = 'zoo';
     cStr2 = 'test';
     
     if(nIntNum1 != nIntNum2)
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] != nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nIntNum1-[ ',itoa(nIntNum1),' ] == nIntNum2-[ ',itoa(nIntNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(nLongNum1 != nLongNum2)
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] != nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST nLongNum1-[ ',itoa(nLongNum1),' ] == nLongNum2-[ ',itoa(nLongNum2),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cChar1 != cChar2)
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] != cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cChar1-[ ',cChar1,' ] == cChar2-[ ',cChar2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(cStr1 != cStr2)
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] != cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cStr1-[ ',cStr1,' ] == cStr2-[ ',cStr2,' ] :DEBUG<',itoa(__LINE__),'>'";
	  
	
     nTestRun = 0;
     }
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  • Hedberg
    Hedberg Junior Member
    vining wrote: »
    In the below tests I see nothing to make me think that the compiler isn't taking the != combination and translating to <>. The only odd thing this test revealed is when I assigned my two chars.

    STACK_VAR CHAR cChar1;
    STACK_VAR CHAR cChar2;

    cChar1 = '';
    cChar2 = '';

    When I print to diagnostics I get:
    Line 23 (17:30:08):: TEST cChar1-[ @ ] & cChar2-[ @ ] :DEBUG<297>

    Not sure what's up with that but everything else regarding != seems to work just like <> with no odd behavior.


    You have two variables each of which is a one-byte integer. I have no idea what happens when you try to assign '' (i.e., nothing) to a one-byte integer. Does it actually change the value stored in the byte in memory referred to?

    When you do the comparison, you're telling the processor to compare the values stored in each of the bytes referred to and I just don't know what those values would be after the assignment to ''.

    Perhaps if you assign equal values to the variables and then try to null them and then compare using != and then assign different one-byte values and then null them and then compare. My suspicion is that the assignment to '' has no effect.

    Otherwise, I think you and I agree on what != is all about. That is, that it can be used interchangeably with <>. We went through all this a couple years ago and that's my recollection. Also, nobody has actually found a case where <> and != give different results, have they?
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  • a_riot42
    a_riot42 AMX Wizard
    I wonder if this was fixed on newer firmware. You might want to try comparing devices as well. Looking at the project where I had the issue, I notice that I switched from != to <> to fix the problem, and was comparing both integers and devices, but don't recall which comparison caused the problem. From that project onward, after seeing this anomaly, I switched to <>. I dented my head from hitting it against the wall for a long time on that one.

    IE:
    define_device
dev vdvDevice = 0:0:0
dev vdvTest = 0:0:0
dev vdvTV = 31001:1:1


define_program
if(vdvTV != vdvDevice )
{
  doSomething()
}

if(vdvTV <> vdvDevice )
{
  doSomething()
}

if(vdvTest != vdvDevice )
{
  doSomething()
}

if(vdvTest <> vdvDevice )
{
  doSomething()
}

    Can you add a device to your test code?
    Paul
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  • vining
    vining X Member
    Code: 
    DEFINE_DEVICE   //VIRTUALS

vdvDevice 		= 0:0:0
vdvTest 		= 0:0:0
vdvTV 			= 31001:1:1

DEFINE_PROGRAM  

if(nTestRun)
     {
     if(vdvTV != vdvDevice)
	  SEND_STRING 0,"'TEST vdvTV-[ ',fnDEV_TO_STRING(vdvTV),' ] != vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST vdvTV-[ ',fnDEV_TO_STRING(vdvTV),' ] == vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(vdvTV <> vdvDevice)
	  SEND_STRING 0,"'TEST vdvTV-[ ',fnDEV_TO_STRING(vdvTV),' ] <> vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST vdvTV-[ ',fnDEV_TO_STRING(vdvTV),' ] == vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(vdvTest != vdvDevice)
	  SEND_STRING 0,"'TEST vdvTest-[ ',fnDEV_TO_STRING(vdvTest),' ] != vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST vdvTest-[ ',fnDEV_TO_STRING(vdvTest),' ] == vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(vdvTest <> vdvDevice)
	  SEND_STRING 0,"'TEST vdvTest-[ ',fnDEV_TO_STRING(vdvTest),' ] <> vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST vdvTest-[ ',fnDEV_TO_STRING(vdvTest),' ] == vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     nTestRun = 0;
}

    results:
    Line      1 (21:04:32)::  TEST vdvTV-[ 31001:1:1 ] != vdvDevice-[ 0:0:0 ] :DEBUG<149>
Line      2 (21:04:32)::  TEST vdvTV-[ 31001:1:1 ] <> vdvDevice-[ 0:0:0 ] :DEBUG<154>
Line      3 (21:04:32)::  TEST vdvTest-[ 0:0:0 ] == vdvDevice-[ 0:0:0 ] :DEBUG<161>
Line      4 (21:04:32)::  TEST vdvTest-[ 0:0:0 ] == vdvDevice-[ 0:0:0 ] :DEBUG<166>
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  • jjames
    jjames AMX Sustaining Engineer
    If anyone has a definitive example showing a discrepancy in the use of != and <>, it would be greatly appreciated in chasing down the answer.
    · Share on FacebookShare on Twitter
  • a_riot42
    a_riot42 AMX Wizard
    vining wrote: »
    Code: 
    DEFINE_DEVICE   //VIRTUALS

vdvDevice 		= 0:0:0
vdvTest 		= 0:0:0
vdvTV 			= 31001:1:1

DEFINE_PROGRAM  

if(nTestRun)
     {
     if(vdvTV != vdvDevice)
	  SEND_STRING 0,"'TEST vdvTV-[ ',fnDEV_TO_STRING(vdvTV),' ] != vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST vdvTV-[ ',fnDEV_TO_STRING(vdvTV),' ] == vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(vdvTV <> vdvDevice)
	  SEND_STRING 0,"'TEST vdvTV-[ ',fnDEV_TO_STRING(vdvTV),' ] <> vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST vdvTV-[ ',fnDEV_TO_STRING(vdvTV),' ] == vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(vdvTest != vdvDevice)
	  SEND_STRING 0,"'TEST vdvTest-[ ',fnDEV_TO_STRING(vdvTest),' ] != vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST vdvTest-[ ',fnDEV_TO_STRING(vdvTest),' ] == vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(vdvTest <> vdvDevice)
	  SEND_STRING 0,"'TEST vdvTest-[ ',fnDEV_TO_STRING(vdvTest),' ] <> vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST vdvTest-[ ',fnDEV_TO_STRING(vdvTest),' ] == vdvDevice-[ ',fnDEV_TO_STRING(vdvDevice),' ] :DEBUG<',itoa(__LINE__),'>'";
	  
     nTestRun = 0;
}

    results:
    Line      1 (21:04:32)::  TEST vdvTV-[ 31001:1:1 ] != vdvDevice-[ 0:0:0 ] :DEBUG<149>
Line      2 (21:04:32)::  TEST vdvTV-[ 31001:1:1 ] <> vdvDevice-[ 0:0:0 ] :DEBUG<154>
Line      3 (21:04:32)::  TEST vdvTest-[ 0:0:0 ] == vdvDevice-[ 0:0:0 ] :DEBUG<161>
Line      4 (21:04:32)::  TEST vdvTest-[ 0:0:0 ] == vdvDevice-[ 0:0:0 ] :DEBUG<166>

    Looking through my code I was using arrays. Not sure if that will make any difference.

    My code looked something like this:

    define_device 
vdvNull = 0:0:0

if(dvDevices[1][1] != vdvNull)
{
  doSomething()
}

    I called the problem into AMX TS so the possibility exists they were able to correct it in a subsequent firmware release. This occurred back in 2009.
    Paul
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  • jjames
    jjames AMX Sustaining Engineer
    My tests

    Here's what I've come up with in testing. Note that a few of the tests were not 100% specific to the question at hand, however, I thought they might be helpful in trying to find a discrepancy in != and <>.

    The code
    http://pastebin.com/dve00sKi

    The results
    Master Type: NI-3100
    Master Firmware: v4.1.373
    Device Firmware: v1.30.10
    http://pastebin.com/Cxr2xg2s

    Master Type: NI-2000
    Master Firmware: v3.50.430
    Device Firmware: v1.13.7
    http://pastebin.com/j808uykY

    I then downgraded the master firmware
    Master Type: NI-2000
    Master Firmware: v2.32.148
    Device Firmware: v1.12.140
    http://pastebin.com/QyD9mM8P


    Unless there is something I missed, which is very possible, I don't see any difference between firmware versions. Perhaps my tests were too weak. I'll be happy to test on an array of firmwares if it means getting to the bottom of this.
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  • RichardHamilton
    RichardHamilton Member
    Personally, I have for forever been using != -- (the symbology works for me as well). It has _NEVER_ failed me.

    I use it in multiple languages. I've never liked using <> .. it reminds me of GWbasic or something. != is always a true C expression for me.

    Never failed as != .. never.

    for example, there are times when I wish to stop an 'if' block from running. So instead of commenting or editing out the block, I'll simply change the qualifier to if(1!=1) and the block will be skipped.

    and the bottom line is, try to avoid 'if' statements. If you are using 'swtich' blocks, then the problem will not arise at all - i believe.

    like others have said, just my 2 cents worth.
    · Share on FacebookShare on Twitter
  • vining
    vining X Member
    RichardHamilton wrote: »
    I'll simply change the qualifier to if(1!=1) and the block will be skipped.
    Wouldn't if(0) be simpler? :)
    · Share on FacebookShare on Twitter
  • RichardHamilton
    RichardHamilton Member
    vining wrote: »
    Wouldn't if(0) be simpler? :)

    yes, of course your right.. i'm talking about a habit that creates a visual guide for me.. i can always recognise why i did something if i used that 1!=1 :)

    bloody programmers, ten thousand one hundred and five million ways to open a bottle top :)
    · Share on FacebookShare on Twitter
  • a_riot42
    a_riot42 AMX Wizard
    Just to muddy the waters further, if != is equivalent to <> then is =! equivalent to <> ?
    Paul
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  • Hedberg
    Hedberg Junior Member
    a_riot42 wrote: »
    Just to muddy the waters further, if != is equivalent to <> then is =! equivalent to <> ?
    Paul

    No, no, no.

    != is a single operator equivalent to the netlinx not equal ccomparative <>. =! Is two separate operators.


    =!, when you are looking at it as a comparative, first executes the !, because of the precedence. Then it does the comparative evaluation. Compare:

    If(2!=3)

    and

    If(2=!3)
    · Share on FacebookShare on Twitter
  • HARMAN_guy.minervini
    HARMAN_guy.minervini AMX Commercial Support
    Obfuscation
    Hedberg wrote: »

    =!, when you are looking at it as a comparative, first executes the !, because of the precedence. Then it does the comparative evaluation.

    Sounds like you could use IF (0=!5) or IF (TRUE =! FALSE) for TRUE statements
    · Share on FacebookShare on Twitter
  • HARMAN_guy.minervini
    HARMAN_guy.minervini AMX Commercial Support
    Failure caused by something else?

    It looks to me like this really boils down to: we have to see the code that invoked the bug. It's entirely possible that something else is causing the problem.
    For example:

    I have recently been bitten by a string evaluation "feature" where only the first byte of the string is used. This happens when a string is used where a number is expected.

    What I was trying to do was check if a string had something in it, and initially wrote the code little too carelessly:
    IF (string)
{
    // do something
}

    The problem was - it sometimes evaluated as TRUE even if the string had no length.

    This compiles fine, and works most of the time.
    What happened was if the first byte of the string was non-0, then it would do something – even if the length of the string was 0.

    This was the fix:
    IF (LENGTH_ARRAY(string))
{
    // do something
}

    Here's another example that uses not-equals operators:
    CHAR str[] = "1,2,3,4,5"

IF (str <> 1)
{
    // do something
}
ELSE
{
   // do something else
}
    Guess what happens?

    p.s. The same thing happens when you do this: 
    IF (str != 1)
{
    // do something
}
ELSE
{
   // do something else
}
    Change the first byte of str to 0 - the other leg will execute.
    · Share on FacebookShare on Twitter
  • a_riot42
    a_riot42 AMX Wizard
    guy.minervini wrote: »
    It looks to me like this really boils down to: we have to see the code that invoked the bug. It's entirely possible that something else is causing the problem.

    That's always a possibility. My memory tells me that I spent a long time testing that code and I ended up having to put a lot of send_strings in there to finally figure it out. I called AMX TS and was told that != isn't actually the correct operator for not equal to, and once I switched to <> the bug disappeared. From what I recall, the bug only occurred for a specific value, so it worked 99% of the time, making it even more difficult to debug. Anyway, if you have total confidence that != works in every case, use it. I'm sticking with <> :)
    Paul
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  • vining
    vining X Member
    guy.minervini wrote: »
    What I was trying to do was check if a string had something in it, and initially wrote the code little too carelessly:
    IF (string)
{
    // do something
}
    Crap, I some times do this too. :(
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  • rynando
    rynando Junior Member
    guy.minervini wrote: »
    I have recently been bitten by a string evaluation "feature" where only the first byte of the string is used. This happens when a string is used where a number is expected.

    What I was trying to do was check if a string had something in it, and initially wrote the code little too carelessly:
    IF (string)
{
    // do something
}

    I think I've seen this happen when a variable is created but not set to any value. If there's something already in the memory allocated for the variable you can get random junk in there which will cause the array to evaluate as true.
    · Share on FacebookShare on Twitter
  • Hedberg
    Hedberg Junior Member
    rynando wrote: »
    I think I've seen this happen when a variable is created but not set to any value. If there's something already in the memory allocated for the variable you can get random junk in there which will cause the array to evaluate as true.

    apparently, if(string) is the same as if(string[1]). If what you want to do is determine if there is any valid value assigned to the string, this doesn't really do the trick. One reason is as already noted -- just because the string has no length doesn't mean that there is a zero value stored in the memory assigned to string[1]. Another problem is that it is perfectly fine to have a valid string with the first element being assigned zero. "0,'this is a valid string',$0d "
    for example.

    Something else that can cause difficulty is using a device array on the right hand side.

    [vdvTPArray,nButton] = ![vdvTPArray,nButton]

    may not give the desired result, for example.
    · Share on FacebookShare on Twitter
  • rynando
    rynando Junior Member
    Hedberg wrote: »
    Another problem is that it is perfectly fine to have a valid string with the first element being assigned zero. "0,'this is a valid string',$0d "
    for example.

    This is a good point. I'll usually check for empty arrays like this:
    if(charArray != '')

    or
    if(length_array(charArray) != 0)
    · Share on FacebookShare on Twitter
  • vining
    vining X Member
    The few times I can think of where I would have taken the lazy man's approach if(string) I would suspect that I was looking for string literals so I'm probably safe. Normally I use the standard methods discussed but I never would has suspected that only the 1st byte was being evaluated.

    Since I had the other test set up still I modified it to help me get my head warapped around this issue and here's what I got: 
    Line      1 (18:17:23)::  Initialized values
Line      2 (18:17:23)::  VOLATILE CHAR cTestStr[5]
Line      3 (18:17:23)::  VOLATILE CHAR cTestStr_Init[5] = {1,2,3,4,5}
Line      4 (18:17:23)::  VOLATILE CHAR cTestStr_Init_0[5] = {0,0,0,0,0}
Line      5 (18:17:23)::  VOLATILE CHAR cTestStr_Init_0_1[5] = {0,1,1,1,1}
Line      6 (18:17:23)::  .
Line      7 (18:17:23)::  TEST cTestStr-[ has no value ] :DEBUG<155>
Line      8 (18:17:23)::  TEST cTestStr_Init-[ has value ] :DEBUG<158>
Line      9 (18:17:23)::  TEST cTestStr_Init_0-[ has no value ] :DEBUG<165>
Line     10 (18:17:23)::  TEST cTestStr_Init_0_1-[ has no value ] :DEBUG<170>
Line     11 (18:17:23)::  .
Line     12 (18:17:23)::  ..
Line     13 (18:17:23)::  ...
Line     14 (18:17:23)::  SET_LENGTH_STRING(cTestStr,5)
Line     15 (18:17:23)::  SET_LENGTH_STRING(cTestStr_Init,0)
Line     16 (18:17:23)::  .
Line     17 (18:17:23)::  TEST cTestStr-[ has no value ] :DEBUG<182>
Line     18 (18:17:23)::  TEST cTestStr_Init-[ has value ] :DEBUG<185>
Line     19 (18:17:23)::  .
Line     20 (18:17:23)::  ..
Line     21 (18:17:23)::  ...
Line     22 (18:17:23)::  cTestStr = "1,2,3,4,5"
Line     23 (18:17:23)::  cTestStr_Init = "1,2,3,4,5"
Line     24 (18:17:23)::  .
Line     25 (18:17:23)::  TEST cTestStr-[ has value ] :DEBUG<197>
Line     26 (18:17:23)::  TEST cTestStr_Init-[ has value ] :DEBUG<202>
Line     27 (18:17:23)::  .
Line     28 (18:17:23)::  ..
Line     29 (18:17:23)::  ...
Line     30 (18:17:23)::  cTestStr = "1,2,3,4,5"
Line     31 (18:17:23)::  cTestStr_Init = "1,2,3,4,5"
Line     32 (18:17:23)::  SET_LENGTH_STRING(cTestStr,5)
Line     33 (18:17:23)::  SET_LENGTH_STRING(cTestStr_Init,5)
Line     34 (18:17:23)::  .
Line     35 (18:17:23)::  TEST cTestStr-[ has value ] :DEBUG<218>
Line     36 (18:17:23)::  TEST cTestStr_Init-[ has value ] :DEBUG<223>
Line     37 (18:17:23)::  .
Line     38 (18:17:23)::  ..
Line     39 (18:17:23)::  ...
Line     40 (18:17:23)::  SET_LENGTH_STRING(cTestStr,0)
Line     41 (18:17:23)::  SET_LENGTH_STRING(cTestStr_Init,0)
Line     42 (18:17:23)::  cTestStr = "0,2,3,4,5"
Line     43 (18:17:23)::  cTestStr_Init = "0,2,3,4,5"
Line     44 (18:17:23)::  .
Line     45 (18:17:23)::  TEST cTestStr-[ has no value ] :DEBUG<241>
Line     46 (18:17:23)::  TEST cTestStr_Init-[ has no value ] :DEBUG<246>
Line     47 (18:17:23)::  .
Line     48 (18:17:23)::  ..
Line     49 (18:17:23)::  ...
Line     50 (18:17:23)::  cTestStr = "0,2,3,4,5"
Line     51 (18:17:23)::  cTestStr_Init = "0,2,3,4,5"
Line     52 (18:17:23)::  SET_LENGTH_STRING(cTestStr,5)
Line     53 (18:17:23)::  SET_LENGTH_STRING(cTestStr_Init,5)
Line     54 (18:17:23)::  .
Line     55 (18:17:23)::  TEST cTestStr-[ has no value ] :DEBUG<262>
Line     56 (18:17:23)::  TEST cTestStr_Init-[ has no value ] :DEBUG<267>
Line     57 (18:17:23)::  .
Line     58 (18:17:23)::  ..
Line     59 (18:17:23)::  ...
Line     60 (18:17:23)::  SET_LENGTH_STRING(cTestStr,5)
Line     61 (18:17:23)::  SET_LENGTH_STRING(cTestStr_Init,5)
Line     62 (18:17:23)::  cTestStr = ''
Line     63 (18:17:23)::  cTestStr_Init = ''
Line     64 (18:17:23)::  .
Line     65 (18:17:23)::  TEST cTestStr-[ has no value ] :DEBUG<283>
Line     66 (18:17:23)::  TEST cTestStr_Init-[ has no value ] :DEBUG<288>
Line     67 (18:17:23)::  .
Line     68 (18:17:23)::  ..
Line     69 (18:17:23)::  ...
Line     70 (18:17:23)::  cTestStr = "0,2,3,4,5"
Line     71 (18:17:23)::  cTestStr_Init = "0,2,3,4,5
Line     72 (18:17:23)::  cTestStr = ''
Line     73 (18:17:23)::  cTestStr_Init = ''
Line     74 (18:17:23)::  SET_LENGTH_STRING(cTestStr,0)
Line     75 (18:17:23)::  SET_LENGTH_STRING(cTestStr_Init,0)
Line     76 (18:17:23)::  .
Line     77 (18:17:23)::  TEST cTestStr-[ has no value ] :DEBUG<308>
Line     78 (18:17:23)::  TEST cTestStr_Init-[ has no value ] :DEBUG<313>
    if anyone wants to modify the test here's the code. 
    DEFINE_VARIABLE //testing

VOLATILE INTEGER nTestRun;

VOLATILE CHAR cTestStr[5];
VOLATILE CHAR cTestStr_Init[5] = {1,2,3,4,5};
VOLATILE CHAR cTestStr_Init_0[5] = {0,0,0,0,0};
VOLATILE CHAR cTestStr_Init_0_1[5] = {0,1,1,1,1};

DEFINE_PROGRAM  

if(nTestRun)
     {
     SEND_STRING 0,"'Initialized values'";
     SEND_STRING 0,"'VOLATILE CHAR cTestStr[5]'";
     SEND_STRING 0,"'VOLATILE CHAR cTestStr_Init[5] = {1,2,3,4,5}'";
     SEND_STRING 0,"'VOLATILE CHAR cTestStr_Init_0[5] = {0,0,0,0,0}'";
     SEND_STRING 0,"'VOLATILE CHAR cTestStr_Init_0_1[5] = {0,1,1,1,1}'";
     SEND_STRING 0,"'.'";
     if(cTestStr)
	  SEND_STRING 0,"'TEST cTestStr-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
    
    if(cTestStr_Init)
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(cTestStr_Init_0)
	  SEND_STRING 0,"'TEST cTestStr_Init_0-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr_Init_0-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
	  
     if(cTestStr_Init_0_1)
	  SEND_STRING 0,"'TEST cTestStr_Init_0_1-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr_Init_0_1-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     SEND_STRING 0,"'.'";SEND_STRING 0,"'..'";SEND_STRING 0,"'...'";
     SET_LENGTH_STRING(cTestStr,5);
     SET_LENGTH_STRING(cTestStr_Init,0);
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr,5)'";
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr_Init,0)'";
     SEND_STRING 0,"'.'";
     
     if(cTestStr)
	  SEND_STRING 0,"'TEST cTestStr-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cTestStr_Init)
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     SEND_STRING 0,"'.'";SEND_STRING 0,"'..'";SEND_STRING 0,"'...'";
     cTestStr = "1,2,3,4,5";
     cTestStr_Init = "1,2,3,4,5";
     SEND_STRING 0,"'cTestStr = "1,2,3,4,5"'";
     SEND_STRING 0,"'cTestStr_Init = "1,2,3,4,5"'";
     SEND_STRING 0,"'.'";
     
     if(cTestStr)
	  SEND_STRING 0,"'TEST cTestStr-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cTestStr_Init)
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     SEND_STRING 0,"'.'";SEND_STRING 0,"'..'";SEND_STRING 0,"'...'";
     cTestStr = "1,2,3,4,5";
     cTestStr_Init = "1,2,3,4,5";
     SET_LENGTH_STRING(cTestStr,5);
     SET_LENGTH_STRING(cTestStr_Init,5);
     SEND_STRING 0,"'cTestStr = "1,2,3,4,5"'";
     SEND_STRING 0,"'cTestStr_Init = "1,2,3,4,5"'";
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr,5)'";
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr_Init,5)'";
     SEND_STRING 0,"'.'";
     
     if(cTestStr)
	  SEND_STRING 0,"'TEST cTestStr-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cTestStr_Init)
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     SEND_STRING 0,"'.'";SEND_STRING 0,"'..'";SEND_STRING 0,"'...'";
     SET_LENGTH_STRING(cTestStr,0);
     SET_LENGTH_STRING(cTestStr_Init,0);
     cTestStr = "0,2,3,4,5";
     cTestStr_Init = "0,2,3,4,5";
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr,0)'";
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr_Init,0)'";
     SEND_STRING 0,"'cTestStr = "0,2,3,4,5"'";
     SEND_STRING 0,"'cTestStr_Init = "0,2,3,4,5"'";
     SEND_STRING 0,"'.'";
     
     if(cTestStr)
	  SEND_STRING 0,"'TEST cTestStr-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cTestStr_Init)
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     SEND_STRING 0,"'.'";SEND_STRING 0,"'..'";SEND_STRING 0,"'...'";
     cTestStr = "0,2,3,4,5";
     cTestStr_Init = "0,2,3,4,5";
     SET_LENGTH_STRING(cTestStr,5);
     SET_LENGTH_STRING(cTestStr_Init,5);
     SEND_STRING 0,"'cTestStr = "0,2,3,4,5"'";
     SEND_STRING 0,"'cTestStr_Init = "0,2,3,4,5"'";
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr,5)'";
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr_Init,5)'";
     SEND_STRING 0,"'.'";
     
     if(cTestStr)
	  SEND_STRING 0,"'TEST cTestStr-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cTestStr_Init)
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
	  
     SEND_STRING 0,"'.'";SEND_STRING 0,"'..'";SEND_STRING 0,"'...'";
     SET_LENGTH_STRING(cTestStr,5);
     SET_LENGTH_STRING(cTestStr_Init,5);
     cTestStr = '';
     cTestStr_Init = '';
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr,5)'";
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr_Init,5)'";
     SEND_STRING 0,"'cTestStr = '''''";
     SEND_STRING 0,"'cTestStr_Init = '''''";
     SEND_STRING 0,"'.'";
     
     if(cTestStr)
	  SEND_STRING 0,"'TEST cTestStr-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cTestStr_Init)
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
	  
     SEND_STRING 0,"'.'";SEND_STRING 0,"'..'";SEND_STRING 0,"'...'";
     cTestStr = "0,2,3,4,5";
     cTestStr_Init = "0,2,3,4,5";
     cTestStr = '';
     cTestStr_Init = '';
     SET_LENGTH_STRING(cTestStr,0);
     SET_LENGTH_STRING(cTestStr_Init,0);
     SEND_STRING 0,"'cTestStr = "0,2,3,4,5"'";
     SEND_STRING 0,"'cTestStr_Init = "0,2,3,4,5'";
     SEND_STRING 0,"'cTestStr = '''''";
     SEND_STRING 0,"'cTestStr_Init = '''''";
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr,0)'";
     SEND_STRING 0,"'SET_LENGTH_STRING(cTestStr_Init,0)'";
     SEND_STRING 0,"'.'";
     
     if(cTestStr)
	  SEND_STRING 0,"'TEST cTestStr-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
     
     if(cTestStr_Init)
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has value ] :DEBUG<',itoa(__LINE__),'>'";
     else
	  SEND_STRING 0,"'TEST cTestStr_Init-[ has no value ] :DEBUG<',itoa(__LINE__),'>'";
	  
     nTestRun = 0;
}
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  • jjames
    jjames AMX Sustaining Engineer
    Don't forget that an IF statement is looking for one of two values, true or false (zero or non-zero).

    That being said, my test results showed that even doing a str = '' or set_length_string(str,0) resulted in a true condition.

    My full test code was uploaded to PasteBin as well as the results in different "bins". (See this post.)

    Here were the tests & results. Note: s_string had a value of '12' prior to Test 30. 
            send_string 0,'Test 30  ************************************';
        s_string = '';
        if(s_string)
                send_string 0,"'s_string == true'";
        else
                send_string 0,"'s_string == false'";
        send_string 0,"'length_string(s_string) == ',itoa(length_string(s_string))";
       
        send_string 0,'Test 31  ************************************';
        set_length_string(s_string,0);
        if(s_string)
                send_string 0,"'s_string == true'";
        else
                send_string 0,"'s_string == false'";
        send_string 0,"'length_string(s_string) == ',itoa(length_string(s_string))";

    Line     91 (19:37:15.798)::  Test 30  ************************************
Line     92 (19:37:15.803)::  s_string == true
Line     93 (19:37:15.806)::  length_string(s_string) == 0
Line     94 (19:37:15.812)::  Test 31  ************************************
Line     95 (19:37:15.814)::  s_string == true
Line     96 (19:37:15.817)::  length_string(s_string) == 0
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  • a_riot42
    a_riot42 AMX Wizard
    rynando wrote: »
    if(length_array(charArray) != 0)

    I think 
    if(length_array(charArray))
    would accomplish the same thing would it not? The != 0 is redundant.
    Paul
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  • rynando
    rynando Junior Member
    a_riot42 wrote: »
    I think 
    if(length_array(charArray))
    would accomplish the same thing would it not? The != 0 is redundant.
    Paul

    Ya but for me the readability is improved by having the != in there.
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