Passing Array in a Funtion

Projects Programming
1

Hi,

I'm trying to pass 2 arrays to a function and sum the elements of each arrray. However, I am getting an error code.

float Sxyz[] = {1.1,2.0,3.25};
float Txyz[] = {2.0,4.45,6.75};
float Nxyz[3];

void setup() {
  // put your setup code here, to run once:
 Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  
  MirrorNormal(Sxyz[],Txyz[],Nxyz[]);
  
  delay(1000);
}


void MirrorNormal(float Sunxyz, float Targetxyz, float ReturnNormal){
  ReturnNormal[0] = Sunxyz[0] + Targetxyz[0];
  ReturnNormal[1] = Sunxyz[1] + Targetxyz[1];
  ReturnNormal[2] = Sunxyz[2] + Targetxyz[2];
  Serial.print(ReturnNormal[0]);Serial.print(",");
  Serial.print(ReturnNormal[1]);Serial.print(",");
  Serial.println(ReturnNormal[2]);
}

This is the error I am getting:
^
exit status 1
expected primary-expression before ']' token

2

Hello

Look at this : C++ Passing Arrays to Functions

3

Why are you passing global variables to a function ?

4

If I create a local variable, how do I return the value? This is demo code whose frame work I will use for a larger code

5

In the normal way, or you could change a global variable. In the code snippet that you posted you did not return a value anyway

6

Don't pass the array, pass a pointer or reference to it. For example:

float Sxyz[] = {1.1,2.0,3.25};
float Txyz[] = {2.0,4.45,6.75};
float Nxyz[3];

void setup() 
{
    // put your setup code here, to run once:
    Serial.begin(9600);
}

void loop() 
{
  // put your main code here, to run repeatedly:
  
  MirrorNormal( Sxyz, Txyz, Nxyz );  
  Serial.print(Nxyz[0]);Serial.print(",");
  Serial.print(Nxyz[1]);Serial.print(",");
  Serial.println(Nxyz[2]);
  delay(1000);
}


void MirrorNormal(float *Sunxyz, float *Targetxyz, float *ReturnNormal)
{
  *ReturnNormal = *Sunxyz + *Targetxyz;
  *(ReturnNormal+1) = *(Sunxyz+1) + *(Targetxyz+1);
  *(ReturnNormal+2) = *(Sunxyz+2) + *(Targetxyz+2);
}
7

Why make things so obscure?

void MirrorNormal(float Sunxyz[], float Targetxyz[], float ReturnNormal[])
{
  ReturnNormal [0] = Sunxyz[0] + Targetxyz[0];
  ReturnNormal [1] = Sunxyz[1] + Targetxyz[1];
  ReturnNormal [2] = Sunxyz[2] + Targetxyz[2];
}
1 Like
8

Or pass the number of elements so the same function can be used with arrays of different sizes:

  MirrorNormal(3, Sxyz, Txyz, Nxyz); 

void MirrorNormal(size_t count, float Sunxyz[], float Targetxyz[], float ReturnNormal[])
{
  for (size_t i=0; i< count; i++)
    ReturnNormal [i] = Sunxyz[1] + Targetxyz[1];
}

And you can make it a function template so it works on arrays of different types, not just 'float'. I think that would look something like:

  MirrorNormal<float>(3, Sxyz, Txyz, Nxyz); 


void MirrorNormal<T>(size_t count, T Sunxyz[], T Targetxyz[], T ReturnNormal[])
{
  for (size_t i=0; i< count; i++)
    ReturnNormal [i] = Sunxyz[1] + Targetxyz[1];
}
9

Did you mean [1] here or [i] ?

10

OOPS! Yes:
ReturnNormal [i] = Sunxyz[i] + Targetxyz[i];

1 Like
11

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