Type of a type
Blitz3D Forums/Blitz3D Programming/Type of a type
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| When I try to create a type with a type as a field, how do I make the inner type initialized from within the type declaration? For instance, in the following code segment, let's say I have something like "a.bst = New bst". For some reason I still have to say "a\root.node = New node" because the bst type isn't creating an instance of the node type like I want it to. How would I do this? I'm trying to make a binary search tree. Type node Field value = 0 Field leftNode.node = New node Field rightNode.node = New node End Type Type bst Field root.node = New node End Type |
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| You can't initialise field in blitz. You need to create the node's elsewhere in your code .. The 'Value' field will initialise to 0 by default as soon as a new type is created though. Not sure what your doing but an example .. Type Node field value field leftnode.node field rightnode.node end type global ROOT.node = NODEcreate() ROOT\LeftNode = NODEcreate( 5 ) ROOT\RightNode = NODEcreate( 7 ) Function NODEcreate.node( Value=0 ) this.node = new node this\value = Value return this end function |
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| Thanks for the response. I wish they could implement initialization inside of type definitions in blitz. Are there any object variable types which are generic and can be used to store ints, float, strings, ect., similar to the Object type in Java? Thanks, Joe |
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| You mean %, # and $ which you can use as type specifier on fields? |
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| Those limit the variable to that type. In Java there's a type called Object. You can assign it an integer, a float, a character, a string, whatever you want to assign it. Java handles it either by deducting what the item most likely is or by typecasting. This gives the freedom to make functions that will work for any type without having to make different functions for each type. In my Java project for a school assignment, I made a class that creates BSTs for the Object type. So I could use that class to make a BST with any type for its elements. So far, I haven't seen many other languages do that because the Object type in Java is costly memory-wise. I hope I'm explaining this well. Here's the Java API for object so you know what I'm referring to: http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Object.html |
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You could also initialize the leftnode/rightnode field in the createnode function:root.Node = CreateNode() Function CreateNode.Node() n.node = new node n\leftnode = new node n\rightnode = new node End Function or Function CreateNode.Node() n.node = new node if n <> first node then n\leftnode = before node if n <> last node then n\rightnode = after node End Function If you want to dereference a custom type, try using Handle(root) (object->integer) and Object.Node(x) (integer->object) As for a generic type, you could convert everything into a string, like this: x$ = 3 ;integer x$ = 3.0 ;float x$ = Handle(object) ;object x$ = "hello" ;string |
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| If the code in the original post worked, it would create a chain reaction that would eat all available RAM, then crash. By creating a new node, two new nodes would be created; those two nodes would cause four nodes to be created; ad nauseum. I wish they could implement initialization inside of type definitions in blitz. Just write your own "constructor" function (as the other posters here have done) and never call New directly. Are there any object variable types which are generic and can be used to store ints, float, strings, ect., similar to the Object type in Java? Using Object() and Handle(), you can use ints to store "pointers" to objects of any Type, but not to primitives such as ints, floats, or strings. One solution would be to create small wrapper Types for each primitive. If you're trying to make a generic BST container, check out the other containers I've already designed in my sig. I don't have a BST, but if I did, its interface would be very similar to my others. |
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| Thanks for the advice. I didn't know I could make constuctor functions for user types. That helps a lot! This whole time I've been passing the nodes as parameters, but constructor functions are much cleaner. Thanks, Joe |
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| I'm having a little trouble with the constuctor functions you mentioned. I'm not sure how to correctly implement it, but here is the original code without using constuctor functions: Function insertInt(this.bst, item) p.node = New node prev.node = New node p = this\root While Not p = Null prev = p If p\theInt < item p = p\rightNode Else p = p\leftNode EndIf Wend If this\root = Null this\root = New node this\root\theInt = item ElseIf prev\theInt < item prev\rightNode = New node prev\rightNode\theInt = item Else prev\leftNode = New node prev\leftNode\theInt = item EndIf End Function I want to make a function that can be called something like this: myBst\insertInt(item) Is there a possible way to do something like this? |
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| That looks like some sort of insertion sort to me. What is it you are trying to do exactly? I'm sure there will be a simpler way of doing this. Cheers Stevie |
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| It inserts an element into the binary tree in such an order that an inorder traversal of the tree results in values in numeric order. So far, I haven't been able to find a simpler way to do it with Blitz's limited command set. At least the function works, though. My main question is about functions in general. Can you make a constructor method for a type like in Java where you say something like myBST.insert(value); |
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Sorry never used Java but something like this?SeedRnd ( MilliSecs() ) Type node Field Value End Type For l = 1 To 20 NODEinsert( Rand( 1, 100 ) ) Next For n.node = Each node Print n\value Next MouseWait End Function NODEinsert( Value ) ;create new node This.node = New node This\Value = value ;find it's position in node list For Crt.node = Each node If Crt <> This If This\Value < Crt\Value Insert This Before Crt Exit EndIf Nxt.node = After Crt If Nxt <> Null If This\Value > Crt\Value And This\Value < Nxt\Value Insert This After Crt Exit EndIf EndIf EndIf Next End Function |
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iamdaman13, your code leaks like a sieve!p.node = New node prev.node = New node New creates objects! Read up on it. Also, to make the function more readable, I'd create the new_node to start with, then go through the process of determining where to place it, instead of creating it in one of three places like you've done above. For example, This has nothing to do with "constructor" functions or automatic initialization of type fields. |
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| I want to make a function that can be called something like this: myBst\insertInt(item) Is there a possible way to do something like this? This isn't possible in Blitz3d. It's just syntactic sugar; it's the same thing as BST_insertInt(myBst, item). |
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