Difference Between = and ==

TurnipTruck · August 2007

Greetings,

I am examining some code. What is the difference between = and ==

Thanks.

ekeppel · August 2007

It is a relational operator that can be substituted with a single = in most cases. You can look up relational operators in NS help to see some info on it.

Correct me if I'm wrong but this is how I've always viewed it:

= is for assignment generally, but can be used in a relational expression also

For example, either of the following lines should work fine:
intMyInt = 1
IF(intMyInt = 1) DoFunction()

== is relational only (boolean expressions)

For example:
IF(intMyInt == 1) DoFunction()

I don't really use the == but it can make the code look better and it is easier to pick out relational expressions since it goes right along with && (AND), || (OR), etc.

--Eric

Chip Moody · August 2007

= can serve two functions, assignment and comparison - I.E.:

X = 3 <-- assign the value of 3 to the variable called X
IF (X = 3) <-- comparison - is one value equal to another?

== is found in more common programming languages, and to the best of my knowledge is simply a "comparison only" function.

IF (X == 3) <-- same as above
X == 3 <-- not an assignment operator, so this will fail to compile

In C, = does assignment only, and using it the way we're used to in Netlinx/Axcess for comparison will cause problems...

- Chip

P.S. Of course, some days I feel nostalgic and miss Pascal syntax, where := is the assignment operator.

usefletch · August 2007

Chip is correct. Netlinx compiler allows both terms. The only place it seems required is in ambiguous code. Where the compiler can not differentiate assignment or comparison.
As a C/C++ programmer, the netlinx compiler allows my normal usage of both to compile just fine.

Joe Hebert · August 2007

I agree with all assessments, however, I believe the correct answer to the original question is...one equal sign. Ok, stupid joke.

This is a tad off topic but you can also drop the = sign(s) for comparison and do something like:

IF(x) //will drop thru if x is anything other than 0.

I don?t know if others consider that proper coding or not.

jjames · August 2007

Joe Hebert wrote:

I agree with all assessments, however, I believe the correct answer to the original question is...one equal sign. Ok, stupid joke.

This is a tad off topic but you can also drop the = sign(s) for comparison and do something like:

IF(x) //will drop thru if x is anything other than 0.

I don’t know if others consider that proper coding or not.

I use that all the time. And I will also do:

IF(!x)
{
  // Do stuff if it is zero
}

Though, when comparing multiple things that need to be zero in order for the IF statement to be true, I typically spell it out like so....

IF(x==FALSE && y==TRUE && z==FALSE)

Rather than saying:

IF((!x) && (y) && (!z))

Though both are identical IF statements. The use of the added parenthesis is helpful / recommended when doing something like the second example.

Also, == NetLinx gives a compiler error when it is used for assignment (for the obvious reasons.)

NMarkRoberts · August 2007

I take this very literal coding rule a step further when dealing with muting, which can be confusing as it is reversed sense (muting on means sound off)

Muted = 1
Unmuted = 0

if (bMicMuted = Muted) etc

DHawthorne · August 2007

I always use == for comparisons, even though a single = may work. It's partly from my C++ background, where using an = for comparisons assigns at the same time, but mostly it's so there can be no possible doubt in case I missed a situation the compiler finds ambiguous.

And yes, If(x) is a a perfectly valid statement - I use that kind of syntax all the time; any non-zero evaluation for x returns as true.

Difference Between = and ==

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