begin

  ! %prim     %byte %integer  %map  %spec   charno( %string(255) s,%integer n )
  
  byteintegermap my charno(string(255) s, integer n)
    result == BYTEINTEGER(ADDR(s)+n)
  end

  string(255) string = "00"

  my charno(string,1) = '1'   ;! <-- does not affect string
  charno(string, 2) = '2'     ;! <-- *does* modify string even though the prim
                               !     declaration is the same as my local one.

  printstring(string); newline  ;! This outputs: 02
  
endofprogram