You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: adimat_stack_prefetch.m
    path of file: ./repos/d2d/arFramework3/ThirdParty/StrucID/adimat/runtime
    
    the code of the file until where you have to start completion: %
% function r = adimat_stack_prefetch(n?)
%
% get/set number of buffer items to prefetch asynchronously.
% This functionality is implemented by setting the environment
% variable ADIMAT_STACK_PREFETCH. This setting applies only to those
% stack implementations with "abuffered" in their name
    
function r = adimat_stack_prefetch(n?)
%
% get/set number of buffer items to prefetch asynchronously.
% This functionality is implemented by setting the environment
% variable ADIMAT_STACK_PREFETCH. This setting applies only to those
% stack implementations with "abuffered" in their name.
%
% adimat_stack_prefetch(n) 
%   - this sets the prefetch value to n. When one buffer is filled
%   from disk with data for immediate consumption, asynchronous reads
%   are dispatched for the n preceding data blocks, if these reads are
%   not queued already.
%
% adimat_stack_prefetch()
%   - this returns the value that is currently set
%
% see also adimat_aio_init, adimat_stack, adimat_stack_buffer_size
%
% This file is part of the ADiMat runtime environment
%
function r = adimat_stack_prefetch(sz)
  envVarName = 'ADIMAT_STACK_PREFETCH';
  if nargin > 0
    r = sprintf('%g', sz);
    setenv(envVarName, r);
  else
    r = getenv(envVarName);
  end