Understanding Arrays

[schamass]

I recently used some variable Arrays in a script when i noticed the following behaviour:

having defined some variables

VarM1, VarM2 : double

then i put them into an Array

VarAr : double Array = [VarM1, VarM2]

i expected that when i wrote

VarM1 = 0.5

then the according array index VarAr[0] would contain the same value, because in my variables definition i used this variable VarM1 as the item [0] of the Array.
I thought that VarAr[0] and VarM1 would always have the same content and only the “addressing” would be a diffrent one… but as it turned out, the variable VarM1 and the content of the Array VarAr[0] are two completely diffrent things which, during run time, don’t have any relationship anymore.

On my search for an answer i found this statement from @dhj

Bug and Odd Behavior with Arrays

GP Script is modeled on the Algol-style (Algol, Pascal, Modula 2) rather than on the C style (C, Java, JavaScript, Lua, etc). In that world, arrays are not pointers. We will investigate that crash though. Thanks so much for reporting it.

Which would perfectly explain the described behaviour…
(But this still is some kind of confusing for me)

[dhj]

@schamass

VarAr : double Array = [VarM1, VarM2]

That statement assigns the value of ‘VarM1’ to VarAr[0] and the value of VarM2 to VarAr[1]. It is not assigning the addresses of those variables – remember that the type of that array is double so the array expects double values at every index.

Consider the following as an analogy

VarAr : double Array = [42, 65]

You could not then write

42 = 0.5

Incidentally, since you didn’t initialize those variable, the actual values in the first two entries of VarAr will be random

[schamass]

Makes perfect sense… thanks for the clarification.