Blitz types.... - BlitzCoder.net

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Socoder -> Blitz -> Blitz types....
Wed, 09 Jul 2008, 14:24
Orion Pax	When you create types and then create a new instance, is that pointer for ALL of that ONE type or can you use another variable to create another hole set of that same type. Can you have more than one set of that type?
Wed, 09 Jul 2008, 14:47
Jayenkai	No, or yes, or no... When you initially create and set to a variable.. This.object Then This = Only that one.. It's not until you change what This points to that it's content changes. So, if you make Array[100].Object, and place each object into it's own slot, then.. Sure, you could then have Array2[100].Object, and call those a second set. But no, if you then For Each the objects, it'll use "Object-All", not "Array-Set" as the list selector. If you get what I mean. You can either Set up ObjectA and ObjectB types, or.. Type Object Field Set Field x,y,whatever End Type And then use This\Set to decide which set it belongs in, and what you're going to do with it. (But that means you're going to do at least one "If/Select" for everything, just to see which set it's in..) -=-=- ''Load, Next List!''
Wed, 09 Jul 2008, 15:34
Orion Pax	so im better off just creating a different type for each set. So if I want an asteroid to blow up into a random set of 3-5 medium asteroids then have each of those blow up into a random set of 3-5 small asteroids. I just might as well then. it would probably make it easier for the collision detection and moving them.
Thu, 10 Jul 2008, 16:58
Scherererer	you shouldn't need separate type lists for all the sizes of asteroids anyway. You can just add a field like "field asteroid_Type" and then make a set of global constant variables "aT_small=0, aT_medium=1, aT_large=2..etc.." and just change its behavior based on the type of asteroid. plus, for collision detection, you can set them to different EntityType's based on size or something. -=-=- YouTube Twitter Computer Science Series: Logic (pt1) (part 2) (part 3) 2's Complement Mathematics: Basic Differential Calculus
Thu, 10 Jul 2008, 17:29
JL235	This is where inheritance and polymorphism fixes the problem. An Asteroid class with several subclasses: SmallAsteroid, MediumAsteroid and BigAsteroid You then only need the one list of Asteroids which contains instances of the subclasses.
Thu, 10 Jul 2008, 18:04
mike_g	Heres an example of how to implement inheritance and polymorphism in Blitz in case you're interested. I dident write it myself. The comments kind of explain whats going on: ;------------------------------------------------------------------------------; ; Introduction: ; Using the Object and Handle commands you can convert from Pointer to Address ; and back, making it possible to create (hardcoded) polymorphic functions, ; handling multiple types of objects passed as parameter. ; The short explanation: ; The Handle( Pointer ) function returns the address of the Object pointer to an ; existing object or instance of a type declaration. ; The Object.Type( Address ) keyword returns a pointer to an object of the ; specified Type at the specified Address. ; E.g. typecasting to and from pointer from and to address. ; The long explanation: ; Imagine a simple Type declaration. Type Struct Field Value% End Type ; We'll need a pointer to and an address of an existing (or unexisting) object ; of the same type. Local PointerToStruct.Struct Local AddressOfPointer% ; Let's create a new object and fill it with something useful. PointerToStruct = New Struct PointerToStruct\Value = 2147483647 ; Now we can convert the pointer to an address and nullify it, making it ; inaccessible. AddressOfPointer = Handle( PointerToStruct ) PointerToStruct = Null ; And to make it accessible again, we reverse the process and zero the address. PointerToStruct = Object.Struct( AddressOfPointer ) AddressOfPointer = 0 ; A pointer can only be used to create, delete or modify the object. One will ; need its address to know where it is exactly. You can only compare pointers to ; pointers and pointers to Null, for a pointer does not contain a value. ; One can pass a pointer to a function as parameter but only if one already ; knows the Type. One cannot pass an unidentified pointer to a function. Which ; also goes for returning pointers. ; However one can pass an address to a function, because an address is an ; integer variable. So giving an example is very similar to the things already ; described above. Function Create_Struct( New_Value% ) Local Pointer_To_Struct.Struct Pointer_To_Struct = New Struct Pointer_To_Struct\Value = New_Value Return Handle( Pointer_To_Struct ) End Function ; The above function simply returns an address of a new object of type Struct. ; And the object contains a new value given as parameter when the function was ; first called. The function call would look like this: Address_Of_Pointer% = Create_Struct( 2147483647 ) ; And then you can pass the Address_Of_Pointer variable to another function: Display_Struct( Address_Of_Pointer ) ; That is also how you can utilitize the use of a polymorphic function. Below ; you will find a complete example of a function that handles typeless objects. ; A polymorph is something that has multiple shapes. A C++ 'void' type is ; amorph, meaning not having any shape, or shapeless. ; As a final note, remember that Object and Handle are keywords, so you don't ; need to write the parentheses (). It just makes for better reading in most ; cases but in the program below all parentheses are omitted where the Object ; and Handle keywords are used. ;<-- ; Various type definitions Type TInteger Field Value% End Type Type TFloat Field Value# End Type Type TString Field Value$ End Type Type TStringS Field Length% Field Value$ End Type Type Enemies1 Field X% Field Y% Field Hungry% Field Scared% End Type Type Enemies2 ; Exactly the same as Enemies1 to show it works here too Field X% Field Y% Field Hungry% Field Scared% End Type ; Here are 3 different versions of the same polymorphic function Function DisplayEntry1( PointerAddress% ) ; Pre-cast: ; First converting (or attempting to convert), also known as 'casting', the ; PointerAddress to a usable Pointer. Also, this is not true casting, it's ; more like 'cheat'-casting :) Local PointerToInteger.TInteger = Object.TInteger PointerAddress Local PointerToFloat.TFloat = Object.TFloat PointerAddress Local PointerToString.TString = Object.TString PointerAddress Local PointerToStringS.TStringS = Object.TStringS PointerAddress Local PointerToEnemies1.Enemies1 = Object.Enemies1 PointerAddress Local PointerToEnemies2.Enemies2 = Object.Enemies2 PointerAddress ; If conversion/casting failed, a Null pointer is the result. Blitz casting ; is very strict, so you can't accidently cast a similar type record. ; If casting was successful, call another function which displays the ; contents of the object. If PointerToInteger <> Null DisplayValue PointerToInteger\Value ElseIf PointerToFloat <> Null DisplayValue PointerToFloat\Value ElseIf PointerToString <> Null DisplayValue PointerToString\Value ElseIf PointerToStringS <> Null DisplayValue Left( PointerToStringS\Value , PointerToStringS\Length ) ElseIf PointerToEnemies1 <> Null DisplayEnemy1 PointerToEnemies1 ElseIf PointerToEnemies2 <> Null DisplayEnemy2 PointerToEnemies2 End If End Function Function DisplayEntry2( PointerAddress ) ; Cast on-the-fly: ; Check if the address can be casted (and exists) first, then create a ; pointer for usage. If Object.TInteger PointerAddress <> Null PointerToInteger.TInteger = Object.TInteger PointerAddress DisplayValue PointerToInteger\Value ElseIf Object.TFloat PointerAddress <> Null PointerToFloat.TFloat = Object.TFloat PointerAddress DisplayValue PointerToFloat\Value ElseIf Object.TString PointerAddress <> Null PointerToString.TString = Object.TString PointerAddress DisplayValue PointerToString\Value ElseIf Object.TStringS PointerAddress <> Null PointerToStringS.TStringS = Object.TStringS PointerAddress DisplayValue Left( PointerToStringS\Value , PointerToStringS\Length ) ElseIf Object.Enemies1 PointerAddress <> Null PointerToEnemies1.Enemies1 = Object.Enemies1 PointerAddress DisplayEnemy1 PointerToEnemies1 ElseIf Object.Enemies2 PointerAddress <> Null PointerToEnemies2.Enemies2 = Object.Enemies2 PointerAddress DisplayEnemy2 PointerToEnemies2 End If End Function Function DisplayEntry3( PointerAddress ) ; Multi-cast: ; Attempt to cast the PointerAddress to a Pointer. Then cast the valid or ; invalid pointer back to a PointerAddress. An invalid pointer, being Null, ; always casts back to a zero address, so this is actually a redundant cast. If Handle Object.TInteger PointerAddress PointerToInteger.TInteger = Object.TInteger PointerAddress DisplayValue PointerToInteger\Value ElseIf Handle Object.TFloat PointerAddress PointerToFloat.TFloat = Object.TFloat PointerAddress DisplayValue PointerToFloat\Value ElseIf Handle Object.TString PointerAddress PointerToString.TString = Object.TString PointerAddress DisplayValue PointerToString\Value ElseIf Handle Object.TStringS PointerAddress PointerToStringS.TStringS = Object.TStringS PointerAddress DisplayValue Left( PointerToStringS\Value , PointerToStringS\Length ) ElseIf Handle Object.Enemies1 PointerAddress PointerToEnemies1.Enemies1 = Object.Enemies1 PointerAddress DisplayEnemy1 PointerToEnemies1 ElseIf Handle Object.Enemies2 PointerAddress PointerToEnemies2.Enemies2 = Object.Enemies2 PointerAddress DisplayEnemy2 PointerToEnemies2 End If End Function ; Display functions Function DisplayValue( Value$ ) ; This is actually another interesting polymorphic function. Blitz ; automatically casts all native types (integer, float, string) when using a ; string as parameter type. Print Value End Function Function DisplayEnemy1( Enemy.Enemies1 ) ; Demonstration specific for Enemies1. If Enemy\Hungry Color 255 , 255 , 0 ElseIf Enemy\Scared Color 255 , 255 , 255 Else Color 255 , 0 , 0 EndIf Text Enemy\X , Enemy\Y , "X" End Function Function DisplayEnemy2( Enemy.Enemies2 ) ; Demonstration specific for Enemies2. Write "2: " Write Enemy\X + " " Write Enemy\Y + " " Write Enemy\Hungry + " " Print Enemy\Scared End Function ; Back to existentials (implementation). Const ScreenSizeX = 640 Const ScreenSizeY = 480 Graphics ScreenSizeX , ScreenSizeY ; Creating an instance of all basic types. Local PInteger.TInteger = New TInteger PInteger\Value = 2147483647 Local PFloat.TFloat = New TFloat PFloat\Value = 0.2147483647 Local PString.TString = New TString PString\Value = "Hey! That was my line." Local PStringS.TStringS = New TStringS PStringS\Value = "No, it's not. The director altered it." PStringS\Length = 13 ; Then calling the same function to display them all. Note that one needs to ; pass a pointer's address to make it virtually typeless. DisplayEntry1( Handle PInteger ) DisplayEntry1( Handle PFloat ) DisplayEntry1( Handle PString ) DisplayEntry1( Handle PStringS ) ; For demonstrational purposes, 10 random enemies. Const Enemies% = 10 Local Counter% Local PEnemy1.Enemies1 Local PEnemy2.Enemies2 For Counter = 1 To Enemies ; Create an enemy of the first enemy type and fill it with random values. PEnemy1 = New Enemies1 PEnemy1\X = Rnd( ScreenSizeX ) PEnemy1\Y = Rnd( ScreenSizeY ) PEnemy1\Hungry = Rnd( 1 ) PEnemy1\Scared = Rnd( 1 ) ; Create an enemy of the second enemy type, copy values from the first enemy ; and modify it to be completely reversed. PEnemy2 = New Enemies2 PEnemy2\X = ( PEnemy1\X + ScreenSizeX/2 ) Mod ScreenSizeX PEnemy2\Y = ( PEnemy1\Y + ScreenSizeX/2 ) Mod ScreenSizeY PEnemy2\Hungry = Not PEnemy1\Hungry PEnemy2\Scared = Not PEnemy1\Scared DisplayEntry1( Handle( PEnemy1 ) ) DisplayEntry1( Handle( PEnemy2 ) ) Next ; And that's all there is to it :) ;--> ; Have fun :D ;------------------------------------------------------------------------------; --v
Thu, 10 Jul 2008, 20:23
Orion Pax	I get it a bit. Basically I am saving the address of the list to a variable. Then moving it back when I need that list again? So once I am done working with 1 list I can convert it to an address and create my other set of asteroids with the same type and then do the same for each one and convert it over as well..... I guess thats what it means....am I making sense?
Thu, 10 Jul 2008, 22:33
Scherererer	Handle and Object are the two coolest undocumented commands in the existence of the blitz language. Well, maybe that and []. -=-=- YouTube Twitter Computer Science Series: Logic (pt1) (part 2) (part 3) 2's Complement Mathematics: Basic Differential Calculus
Thu, 10 Jul 2008, 23:19
Jayenkai	Handle and Object?! Goes hunting Becomes baffled.. Some day I'll probably find a use for all of that! -=-=- ''Load, Next List!''
Fri, 11 Jul 2008, 18:39
Forklift_Fred	Sounds useful but I wish people wouldn't write such over complicated examples I may read through it properly when I actually have time... -=-=- Come rain or shine...
Fri, 11 Jul 2008, 19:19
Scherererer	In the past, I've used it to reference one type from within another. Think of like, pikman for example: you've got one guy with a bunch of little pikman following him around; so you'd reference all the pikman as handles from the space man's type as a field. -=-=- YouTube Twitter Computer Science Series: Logic (pt1) (part 2) (part 3) 2's Complement Mathematics: Basic Differential Calculus
Sat, 12 Jul 2008, 11:23
9572AD	Of course if you use BlitzMax it's all different -=-=- All the raw, animal magnetism of a rutabaga.
Sun, 13 Jul 2008, 11:49
Forklift_Fred	Found a much simpler Handle and Object example/explanation on BlitzBasic.com (at the bottom of the page) "Ross C" Type weapon Field name$ End Type w.weapon = New weapon w\name$ = "1st weapon - gun" w.weapon = New weapon w\name$ = "2nd weapon - gun" w.weapon = New weapon w\name$ = "3rd weapon - gun" w.weapon = New weapon w\name$ = "4th weapon - gun" w_handle = Handle w.weapon w.weapon = New weapon w\name$ = "5th weapon - gun" w.weapon = New weapon w\name$ = "6th weapon - gun" w.weapon = Object weapon(w_handle) Print w\name$ --v This code creates 6 weapon objects in a type collection. It saves the handle to the 4th type object. Then at the end, jumps back to the 4th object by setting w.weapon to the w_handle (handle of the 4th weapon) What this means is you can store these in an array. For instance, store all the handles to your weapons. When you want a particular weapon, 5 for instance, get the 5th handle in the array and plug it into w.weapon = Object weapon(handle_array(5)) --v weapon - being the type collection Object - being the Blitz command for this process handle_array(5) - being the 5th handle in the array you created. Other uses of this are, storing the handle inside the EntityName() of an entity. e.entity = new entity e\mesh = loadmesh("mymesh.b3d") NameEntity e\mesh, Handle e.entity --v This way, when ever say you shoot an entity, and you use linepick, for example. You get the picked entity, the one you just shot. You grab that entities EntityName(). This contains the handle to the type object it's stored in. You can now modify that enemies health and such. e.entity = Object entity(EntityName(PickedEntity)) --v This shows that it is like a bookmark system, which is what I thought but it wasn't clear before. -=-=- Come rain or shine...
Sun, 13 Jul 2008, 12:25
flying_cucco	As an aside, and for our snakey friends, Handle and Object are ItemInList and IndexedItem respectively.