I am trying to use a function in a custom shader in my post processing material, but whenever I try to compile it says

The shader code is:

```
float4 Kuwahara(float2 uv2){
//float version of the radius
float r = float(radius);
//array of the averages for each pixel region
float3 avg[4];
avg[0] = float3(0.0f, 0.0f, 0.0f);
avg[1] = float3(0.0f, 0.0f, 0.0f);
avg[2] = float3(0.0f, 0.0f, 0.0f);
avg[3] = float3(0.0f, 0.0f, 0.0f);
//array of the standard deviaitons for each pixel region
float3 std[4];
std[0] = float3(0.0f, 0.0f, 0.0f);
std[1] = float3(0.0f, 0.0f, 0.0f);
std[2] = float3(0.0f, 0.0f, 0.0f);
std[3] = float3(0.0f, 0.0f, 0.0f);
//the offsets for each reigon to sample over
float2 offs[4];
offs[0] = float2(-r, 0.0f);
offs[1] = float2(-r, 0.0f);
offs[2] = float2(0.0f, -r);
offs[3] = float2(0.0f, 0.0f);
//position and color holders
float2 p;
float3 col;
//loop through each region
for(int i = 0; i < 4; i++){
//for each x
for(int x = 0; x <= radius; x++){
//for each y
for(int y = 0; y <=radius; y++){
//the positon is each pixel within each region i
p = float2(float(x), float(y)) + offs[i];
//the uv2 position of the pixel to sample is the base uv2 plus the pixel offset
float2 uvp = uv2 + (p / iResolution);
//sample the texture at that position
col = SceneTextureLookup(uvp, 14, false).rgb;
//add in the color to the average color of the region
avg[i] += col;
//add the standard deviation of this color from the region color
std[i] += col * col;
}
}
}
//the total number of pixels that were sampled
float n = pow(r + 1.0f, 2.0f);
//holder for the lowest value
float minV = 1.0f;
//holder for the standard deviation of the corresponding lowest value
float stdf;
for(int i = 0; i < 4; i++){
//make the average colors actually averaged (the are simply sums right now)
avg[i] /= n;
//calculate standard deviation according to standard deviation formula
std[i] = abs((std[i] / n) - (avg[i] * avg[i]));
//sum the standard deviation of each rgb value for this region
stdf = std[i].r + std[i].g + std[i].b;
//if this region's standard deviation is the lowest then use it
if(stdf < minV){
//record this standard deviation
minV = stdf;
//select the value with the lowest standard deviation
col = avg[i];
}
}
return col;
}
float4 main(){
float2 off = 1.0f / iResolution;
float2 right = float2(off.x, 0.0f);
float2 up = float2(0.0f, off.y);
float4 c1 = Kuwahara(uv);
float4 c2 = Kuwahara(uv + right);
float4 c3 = Kuwahara(uv + up);
return (c1 - c2) + (c1 - c3);
}
main();
```

Why is this happening?