1. Re: ABS & recursion
>function call overhead... having to push and pop all those
>newly created/destroyed local duplicate variables is simply
>a clock-tick eater and there ain't much can be done...
>recursion without pushing/popping? then you have something.
>and euphoria would really shine then...
>kinda makes ya wonder what ol' wirth is up to indeed?
When a function calls itself (recursion) cant Euphoria inline a sort of new
non-recursive algorithm in their.. most compilers have an option for
end-tail-recursion, why not Euphoria ?
Off course many of the push and pop overhead remains, however, not all
arguments, declarations, etc. have to be done everytime, esspecially because
they are allready done. I dont exactly know what Im talking about, but I
figure you can emulate recursion:
function bla (sequence s)
if length(s) then
s[1] = s[1] + 1
return s[1] & bla(s[2..length(s)])
else
return s
end if
end function
-- That was a recursive one..
-- This one does preciously the same:
function bla (sequence s)
for index = 1 to length(s)
s[index] = s[index] + 1
end for
return s
end function
-- And now one using EUphoria's auto-recursion (which off course must
*never* be slower than recursion programmed in Euphoria code, as with the
ABS function timings!)
function bla (sequence s)
return s + 1
end function
My point here was, we've been trying to manage to do ABS (for example) with
real-recursion, the auto-recursive operands, but we can also try to do it
without recursion:
This example is tested.. not just writing inside my mailer!
Its a recursive ABS function, that doesnt do any function call at all
(except for a few built-in) and it doesnt use any auto-recursive operators.
-- An demonstration of how to simulate recursion....
-- I havent timed it, but take my word for it, its * SLOW *
-- Have with it ya'all... just remember standard disclaimer applies..
-- Ralf Nieuwenhuijsen (nieuwen at xs4all.nl)
function abs (object x)
sequence hold
object subject
integer flag, start
if atom(x) then
if x < 0 then return -x else return x end if
end if
hold = {}
start = 1
while 1 do
flag = 1
for index = start to length(x) do
subject = x[index]
if atom(subject) then
if subject < 0 then x[index] = -subject end if
else
hold = append(hold, {x, index})
x = x[index]
flag = 0
start = 1
exit
end if
end for
if flag then
if length(hold) then
start = hold[length(hold)][2]
hold[length(hold)][1][start] = x
start = start + 1
x = hold[length(hold)][1]
hold = hold[1..length(hold)-1]
else
return x
end if
end if
end while
end function
