1. Re[2]: Return from nested subroutines (still goto discussion)
- Posted by akusaya at gmx.net
Nov 12, 2004
D> for i = 1 to 5 do
D> *code*
D> end for
D> puts(1, "success\n")
D> puts(1, "program end\n")
D> procedure r(integer x)
D> if x = 5 then
D> puts(1, "success")
D> else
D> r(x+1)
D> end if
D> end procedure
D> procedure main()
D> r(1)
D> puts(1, "program end")
D> end procedure
Thank you, but...
Maybe my code was too much simplified. What I meant is algorithms such
as backtracking or permutation. Now modified example:
object d
d = {0,0,0,0,0}
procedure r(integer x, integer y)
d[x] = y
if x = 5 then
if d[1]+d[2]+d[3]+d[4]+d[5] = 10 then
puts(1, "success")
-- (print d here)
goto ok
end if
else
for i = 0 to 3 do
r(x+1, i)
end for
end if
end procedure
procedure main()
for i = 0 to 3 do
r(1, i)
end for
ok:
puts(1, "program end")
end procedure
Now the purpose of the program is to search d so that sum(d) = 10 and
every element of d is from 0 to 3. But when a solution is found, it
will just print the first solution found and continue to printing
"program end".
Now how can it modified to use no GOTO and no decrease on performance?
(using flags to indicate whether a solution has been found would
decrease performance, I think)
2. Re: Re[2]: Return from nested subroutines (still goto discussion)
> Now the purpose of the program is to search d so that sum(d) = 10 and
> every element of d is from 0 to 3. But when a solution is found, it
> will just print the first solution found and continue to printing
> "program end".
>
> Now how can it modified to use no GOTO and no decrease on performance?
> (using flags to indicate whether a solution has been found would
> decrease performance, I think)
Does this work? I got x = 5 and y = 3. The trick is to use functions
and pass down a 'success' value, like here I use 1 for success, 0 for
failure. Whenever there is a success (or 1) I exit the current loop
and/or return. I've actually gotten used to this style of coding and I
prefer it over goto. This just seems more logical that jumping around
code all willy-nilly.
sequence d
d = {0,0,0,0,0}
function sum( sequence x )
-- calculate the sum of
-- all values in x
atom val
val = 0
for i = 1 to length(x) do
val += x[i]
end for
return val
end function
function r(integer x, integer y)
d[x] = y
if x = 5 then
if sum(d) = 10 then
printf(1, "x = %d\ny = %d\n", {x,y})
puts(1, "success\n")
return 1
end if
else
for i = 0 to 3 do
if r(x+1, i) then
return 1
end if
end for
end if
return 0
end function
procedure main()
for i = 0 to 3 do
if r(1, i) then
exit
end if
end for
puts(1, "program end\n")
end procedure
main()
