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StixandRox

Tue Feb 27, 2007 9:07 pm


Pointer help!?

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I was doing the pointer tut and I get it, and I'm trying to do previous. It works alll the way until you get to 2 and it won't goto one. I know i'm close, but if you can give me a suggestion or another way to look at it that would be great.

var list : collection of
    record
        num : int
        next : ^list
        prev : ^list
    end record
var root : pointer to list %Start of the list
new list, root

var temp, temp2 : pointer to list
var ref : pointer to list %reference

ref := root
new list, temp
ref -> next := temp
ref -> prev := temp
ref -> num := 1
ref := temp

for i : 2 .. 100
    temp2 := temp
    new list, temp
    ref -> next := temp
    ref -> num := i
    ref := temp
    ref -> prev := temp2
end for

ref := root
put ref -> num
ref := list (ref).next %2
put ref -> num
ref := ref -> next %3
put ref -> num
ref := ref -> next %4
put ref -> num
ref := ref -> prev %3
put ref -> num
ref := ref -> prev %2
put ref -> num
ref := ref -> prev %1
put ref -> num

The comment tells it what that line will make it (should make it) go to.

EDIT
When I put the line;
    ref -> prev := temp2
After the ref -> next := temp2 line it gives me all 4's...

EDIT2
for i : 2 .. 100
    ref -> prev := temp
    new list, temp
    ref -> next := temp
    ref -> num := i
    ref := temp
end for
This should work in my mind. It stores the reference in the previous (so at the beggining var list : collection of
    record
        num : int
        next : ^list
        prev : ^list
    end record
var root : pointer to list %Start of the list
new list, root

var temp, temp2 : pointer to list
var ref : pointer to list %reference

ref := root
new list, temp
ref -> next := temp
ref -> prev := temp
ref -> num := 1
ref := temp

for i : 2 .. 99
    temp2 := temp
    new list, temp
    ref -> next := temp
    ref -> num := i
    ref -> prev := temp2
    ref := temp
end for
ref -> num := 100
ref -> next := temp
ref -> prev := temp2

ref := root
for i : 1 .. 100
    put ref -> num
    ref := ref -> next
end for


loop
    ref := ref -> prev     %3
    put ref -> num
end loop
ref := ref -> prev     %2
put ref -> num
ref := ref -> prev     %1
put ref -> num

GAH I reall thought this would work but I gots nothin x_X The prev just makes it 99 everytime (it does go back from 100 though haha)
This is tricky tricky...still working on it ^^;