OpenEuphoria

Re: splitting sequences

• Posted by Andy Serpa <ac at onehorseshy.com> Nov 28, 2004
• 493 views

Jacen wrote:
> 
> Thanks cklester, I shoulda seen that. But now I have another problem.
> I have a procedure exec_cmd that tests if the cmd is in the keywords 
> sequence.If it doesn't find it there, then it splits the input, and tests
> the first string(cmd[1]). But when it returns from the split procedure, cmd
> changes back to what it was before it was splitted. See code below. Is this 
> another simple soultion I have overlooked again? 
> 
> }}}
<eucode>
> 
> global procedure split_cmd(sequence local_cmd)
>   integer j
>   sequence w
>   
>   j = find(' ', cmd)
>   if j > 0 then
>     w = cmd
>     cmd = {{},{}}
>     cmd[1] =w[1..j-1]
>     cmd[2] = w[j+1..length(w)]
>   end if
> end procedure    
> 
> while 1 do
> 
>   cmd = gets(0)
>   cmd = cmd[1..length(cmd)-1]-- take off last character(\n)
>     cmd_loc = find(cmd, keywords) 
>   if cmd_loc > 0 then
>     if cmd_loc > 1 and cmd_loc < 8 then  -- if player is moving, let
>     move_self() handle it
>       move_self(cmd)
>       cur_loc = Tatooine[x][y]
>       num_exits = length(cur_loc[exits])
>       look()
>     elsif cmd_loc = find("look",keywords) then
>       look()
>     end if
>   end if
>   split_cmd(cmd)
>   if length(cmd) = 2 then 
>     if equal(w[1],"greet") then 
>       if find(w[2], cur_loc[people][NAME]) then
>         puts(1, cur_loc[people][GREET_RESP])
>       end if
>     end if
>   end if
> 
> end while
> </eucode>
{{{

> 

In Euphora everything is "passed by value", so when the procedure split_cmd
alters the value of cmd, it only does so locally, within the scope of that
procedure only (because cmd is declared as a parameter).  So there are two
solutions.  Declare "cmd" globally somewhere above the procedure split_cmd, and
don't use a parameter at all in your procedure.  For instance:

sequence cmd
global procedure split_cmd()
  integer j
  sequence w
  
  j = find(' ', cmd)
  if j > 0 then
    w = cmd
    cmd = {{},{}}
    cmd[1] =w[1..j-1]
    cmd[2] = w[j+1..length(w)]
  end if
end procedure 


The other, and possibly better solution, is to make split_cmd a function, so it
returns the altered copy of cmd:

global function split_cmd(sequence cmd)
  integer j
  sequence w
  
  j = find(' ', cmd)
  if j > 0 then
    w = cmd
    cmd = {{},{}}
    cmd[1] =w[1..j-1]
    cmd[2] = w[j+1..length(w)]
  end if

  return cmd

end function 

And then alter the call in the loop to:

cmd = split_cmd(cmd)

I see now that you are using "w" in the loop as well below the call the
split_cmd, but you also declare w in the split_cmd procedure locally.  Which
means that the line:

if equal(w[1],"greet") then

will fail because the program has no knowledge of w at that point.  You would
need to declare w outside the procedure split_cmd as well...