loop to sum array returns address like reading instead of the correct answer. why? - forth

Question

I'm trying to make a program that will sum an array for me, but it keeps on giving me a really long number resembling an address when I try to run the word sum. I tried taking it apart and running it line by line outside of the word in the terminal and manually looping worked fine, but it totally fails when I go to actually make it work. what am i doing wrong?
variable length \ length var declared
create list \ space for my list made
0 variable cumsum \ sum value initialized to zero
: upload ( n1 n2 n3 --) \ loops thru and stuffs data into array
depth ( n1 n2 n3 -- n1 n2 n3 depth) \ get depth
length ! ( n1 n2 n3 depth -- n1 n2 n3) \ array length stored
list ( n1 n2 n3 -- n1 n2 n3 addr)
length # ( n1 n2 n3 addr -- n1 n2 n3 addr nlength)
cells allot ( n1 n2 n3 addr nlength -- n1 n2 n3)
length # 1+ ( n1 n2 n3 -- n1 n2 n3 nlength) \ consume all entries
0 ( n1 n2 n3 nl -- n1 n2 n3 nl 0) \ lower loop parameter..
do ( n1 n2 n3 nl 0 -- n1 n2 n3) \ loop begins
list ( n1 n2 n3 -- n1 n2 n3 addr)
I ( n1 n2 n3 addr -- n1 n2 n3 addr I) \ calculating address
cells ( n1 n2 n3 addr I -- n1 n2 n3 addr Ibytes)
+ ( n1 n2 n3 addr Ibytes -- n1 n2 n3 addr1+)
! ( n1 n2 n3 addr1+ -- n1 n2) \ storing into calculated address
loop
;
upload works like a charm, but then I go to use this word after
: sum ( n1 n2 n3 -- nsum)
upload \ initiates the array
length # \ invokes upper limit of loop
0 \ lower limit of loop
do
list ( -- addr) \ addr invoked
I cells + ( addr -- addr+) \ offset calculated and added
# ( addr+ -- nl) \ registered value at address fetched
cumsum # ( nl -- nl ncs) \ cum sum value fetched to stack
+ ( nl ncs -- nsum) \ summation
cumsum ! ( nsum --) \ new sum written to cumsum
loop
cumsum ? ( -- cumsum) \ show sum
;
and it returns a really long number that looks like an address, and not the sum of some list of small numbers that I add to test it with.
1 ok
2 ok
3 ok
sum 140313777201982 ok

Answer 1

So if I understand correctly, the problem is to:
Store all numbers on the stack into an array.
Sum all numbers stored in an array.
I would do something like this:
: upload ( ... "name" -- ) create depth dup , 0 ?do , loop ;
: sum ( a -- n ) 0 swap #+ 0 ?do #+ rot + swap loop drop ;
Use like this:
1 2 3 4 upload array
array sum .

Answer 2

In UPLOAD you execute LIST LENGTH # CELLS ALLOT. ALLOT allocates memory at the current dictionary or data space pointer, not necessarely at the address returned by LIST. ALLOT does not consume a start address from the stack. Actually the returned address by LIST in the above code snippet is used later by ! in your array filling loop. It's the data for the first array cell. Hence your address like number returned by SUM.
Best is to keep CREATE and ALLOT together. Some dictionary additions occured between the creation of LIST and executing ALLOT. Your array cells might not be where LIST is pointing.
In general variables don't consume a number from the stack. Most of the time they're automaticly initialised to 0. So 0 VARIABLE CUMSUM will a leave zero on the stack.
This has concequences for DEPTH and thus LENGTH, if you run or type the code in one go.
Try to avoid DEPTH, better is to explicitly tell array defining words how many items you want, example: CREATE LIST 3 CELLS ALLOT
BTW running your code as is in SwiftForth, I allocate a 4 cell array right after the dictionary entree for SUM. I store 5 items ( LENGTH # 1+ in UPLOAD ) in the dictionary right after LIST, overwriting parts of the dictionary entree for CUMSUM ...
Lars Brinkhoff shows a nice alternative, apart from DEPTH that is ;-)

Answer 3

The main problem was as #roelf explained. I'll just add two points of interest.
1) How could you know that something was off? When you have a problem like this, examine the memory - do a hex dump!
1 2 3 sum -1223205794 ok
list 32 dump
B7175C58: 58 5C 17 B7 03 00 00 00 - 02 00 00 00 01 00 00 00 X\..............
B7175C68: 00 00 00 00 00 00 00 00 - 5E 5C 17 B7 58 5C 17 B7 ........^\..X\..
ok
You can see that the first cell of list is garbage. So maybe upload wasn't working so well after all!
2) Note that if you just want to add all values on the stack, you don't need to clutter the namespace with variables:
: sum depth 1 do + loop ;