recursion - F# Recursively creating a int list list -

Then I have a bitmap that is an int list list, representing 3 pixels per indicator RGB. One line of the image is a list, and I'm trying to edit this int listing list recycle and spit the second int list list back. The problem is that when I reach the end of a line, I want to make it a second list. Now the code creates a list per pixel per line, 3 values ​​per list and the image is going down a straight line, so it is making a new list of each recursive call I want to continue on the same list, while it The end of the width has not been reached Here's the code to make a bit more sense as I have a hard time explaining this.

  REC grayscale picture (width: integer, width: integer, image: int list list) = image with match | [] - & gt; [] | _ - & gt; Let's get R = image.Have go.Come on. Image.Read.Sit.Cheat.Come on.Come on.Sit.Bell.You average = (int) ((R + G + B) / 3) Give wide bravery and GT; 3 then [average; Average; Average] :: grayscale image (width, width-1, image. Tail, tail) other ??? Firstly, if a new list is created after that, then I want to keep it on the list of averages. (This image is in scaling of BTD) and then I know that it should do it. If that happens then something happens, but probably not at all. I am very confused about doing this.  
  REC BuildRowGrayscale (Column: Int, A: IT) = There is some progress with match calls:  
 Edit: with. 0 - & gt; [] | _ - & gt; A :: a :: a :: BuildRowGrayscale (cols-1) Match image with a Rick Rick GrasecaleImage (width: int, height: int, depth: int, image: int list list) = | [] - & gt; [] | _ - & gt; Let's R = Image. G = image. Take care.Bell.Come on.Better image.Get up.Sit. Sit down. Average = (intestine) ((r + g + b) / 3) (buildreve grayscale width avg) :: grayscale image (width, height, depth, image. Tail)  
 
 but it BuildRowGrayscale (Columns-1)  refuses to build on  (BuildRowGrayscale width average)  and  "This value is not a function and it can not be applied"   
 
 
 After your comment, I think you are trying to do this:  
  REC grayscale image image A. = REC BuildRowGrayscale = FUNCTION | [] - & gt; [] | R :: G :: B :: rest - & gt; Give Avg = (r + g + b) / 3 (avg :: avg :: avg :: BuildRowGrayscale rest). _ - & gt; Failed image with "illegal image" match [] - & gt; [] | Line :: rest - & gt; BuildRowGrayscale line :: grayscale image balance  
 
 or  list.replicate  and  List.map  using: 
 
  grayscale image = REC BuildRowGrayscale = function | Please [] - & gt; [] | R :: G :: B :: rest - & gt; List Repetition 3 ((R + G + B) / 3) @ BuilderGraz balance. _ - & gt; Failed image "List.map BuildRowGrayscale  
 
 Sorry, but the fact that you were specifying width, I think you were also changing the original structure, but if the structure does not change You do not have to specify the width, it is rooted in the original structure.