The head of the DepthFirst procedure is:
proc {DepthFirst Tree Level LeftLim ?RootX ?RightLim}
The question mark "?" marks parameters as output parameters, so you
should pass unbound variables for RootX and RightLim.
If you don't care for the result of these parameters, just call it like
this:
{DepthFirst MyTree2 0 0 _ _}
DepthFirst is a procedure with side effects. In assigns values to the X
and Y fields in "Tree".
As far as I can see, the actual tree painting code is not contained in
the book. But you can of course inspect the resulting data structure with
{Browse MyTree2}
If you want to implement the tree painting, take a look Qtk (see Chapter
10) and its canvas widget.
Hope this helps,
Wolfgang
Emre Sevinc wrote:
I'm reading "Concepts, Techniques, and Models of Computer
Programming" and on page 160 I saw the code to draw a tree and I
wanted to run it on my system I've added those two lines to the end of
code given in the book:
MyTree = tree(key:a val:111
left:tree(key:b val:55
left:tree(key:x val:100
left:tree(key:z val:56 left:leaf right:leaf)
right:tree(key:w val:23 left:leaf right:leaf))
right:tree(key:y val:105 left:leaf
right:tree(key:r val:77 left:leaf
right:leaf)))
right:tree(key:c val:123
left:tree(key:d val:119
left:tree(key:g val:44 left:leaf right:leaf)
right:tree(key:h val:50
left:tree(key:i val:5 left:leaf
right:leaf)
right:tree(key:j val:6 left:leaf
right:leaf)))
right:tree(key:e val:133 left:leaf right:leaf)))
MyTree2 = {AddXY MyTree}
{Browse {DepthFirst MyTree2 3 4 5}}
When I fed the buffer I received the following message:
%***************************** failure **************************
%**
%** Tell: 95 = 5
%**
%** Call Stack:
%** procedure 'DepthFirst' in file "c:/Documents and
Settings/Emre/Desktop/tree.oz", line 20, column 0, PC = 18888300
%**--------------------------------------------------------------
I'm a little bit confused now, I couldn't understand what I should do
to get something similar to the screenshot given in the Figure 3.19 of
the book.
Maybe I'm using the DepthFirst procedure in the wrong way or maybe the
parameters I have passed are wrong, or maybe it is because DepthFirst
is a procedure not a function (but I simply couldn't understand where
its output goes or what the output is, another tree, how it should be
graphically drawn, etc.)
What is the correct way of drawing the actual graphics for the tree?
_________________________________________________________________________________
mozart-users mailing list
[email protected]
http://www.mozart-oz.org/mailman/listinfo/mozart-users
