Exiting Case/select statements

[_PJ_]

Hi

Admittedly I've not read all the various replies on this topic, but I can tell you, that, as mentioned it is not necessary to break from case statements as only TRUE cases are evaluated.

However, if you for example have some extra specific logic for specific cases that may not warrant their own Case (because they share a lot of other functions otherwise) then you can use Exit as aa 'break' from the Select:


Select (n)
Case 0
 .
Case 1,2,3,4,5
   DoTheThingsForAll5Cases()
  If (n Mod 2) Then Exit
  DoSomethingElseThatOnlyAppliesTo2and4()
Case 6
.
Case 7
.
Default
...
[/code]

I find if you have largenumbers of  Select clause, you can save some process by grouping them such as:

Code: [Select]

if (n < 33)
 Select (n)
   Case 0
   ...
  Case 32
 End Select
Else if (n>66)
 Select (n)
  Case 67
  ...
  Case 69

 End Select
Else
 Case 33
 ...
 Case66
End if


By expanding on this principle, you can make an effective binary tree to drastically reduce the number of "Checks" made to identify the Selected value and speed up the processing.

[Baggey]

After a bit of experimenting, I've discovered that reflection is slower than I originally thought.  About 3.5x slower than using Select/Case.  But using function pointers in an array was fastest taking 1/3 the time of Select/Case.

Reflection and Function Pointers dosent really mean anything to me 

So is this something like a function pointer?

Yes it's a different dialect of Basic and the dreaded GOTO/GOSUB  is in there 

Code: [Select]

psub oo_opcode(op_byte)

on op_byte gosub op_0,op_1,op_2,op_3,op_4,op_5,op_6,op_7,op_8,op_9,op_10,op_11,op_12,op_13,op_14,op_15,op_16,op_17,op_18,op_19,op_20,op_21,op_22,op_23,op_24,op_25,op_26,op_27,op_28,op_29,op_30,op_31,op_32,op_33,op_34,op_35,op_36,op_37,op_38,op_39,op_40,op_41,op_42,op_43,op_44,op_45,op_46,op_47,op_48,op_49,op_50,op_51,op_52,op_53,op_54,op_55,op_56,op_57,op_58,op_59,op_60,op_61,op_62,op_63,op_64,op_65,op_66,op_67,op_68,op_69,op_70,op_71,op_72,op_73,op_74,op_75,op_76,op_77,op_78,op_79,op_80,op_81,op_82,op_83,op_84,op_85,op_86,op_87,op_88,op_89,op_90,op_91,op_92,op_93,op_94,op_95,op_96,op_97,op_98,op_99,op_100,op_101,op_102,op_103,op_104,op_105,op_106,op_107,op_108,op_109,op_110,op_111,op_112,op_113,op_114,op_115,op_116,op_117,op_118,op_119,op_120,op_121,op_122,op_123,op_124,op_125,op_126,op_127,op_128,op_129,op_130,op_131,op_132,op_133,op_134,op_135,op_136,op_137,op_138,op_139,op_140,op_141,op_142,op_143,op_144,op_145,op_146,op_147,op_148,op_149,op_150,op_151,op_152,op_153,op_154,op_155,op_156,op_157,op_158,op_159,op_160,op_161,op_162,op_163,op_164,op_165,op_166,op_167,op_168,op_169,op_170,op_171,op_172,op_173,op_174,op_175,op_176,op_177,op_178,op_179,op_180,op_181,op_182,op_183,op_184,op_185,op_186,op_187,op_188,op_189,op_190,op_191,op_192,op_193,op_194,op_195,op_196,op_197,op_198,op_199,op_200,op_201,op_202,op_203,op_204,op_205,op_206,op_207,op_208,op_209,op_210,op_211,op_212,op_213,op_214,op_215,op_216,op_217,op_218,op_219,op_220,op_221,op_222,op_223,op_224,op_225,op_226,op_227,op_228,op_229,op_230,op_231,op_232,op_233,op_234,op_235,op_236,op_237,op_238,op_239,op_240,op_241,op_242,op_243,op_244,op_245,op_246,op_247,op_248,op_249,op_250,op_251,op_252,op_253,op_254,op_255

return

op_0:  // NOP

nxtpc=1

if monitormode=true

if hex_or_dec = false
// Decimal representation
text 1200,placeopcodeslne,digits$(pc,5)
text 1270,placeopcodeslne,digits$(op_byte,3)
text 1460,placeopcodeslne,"NOP"
else
// Hex representation
text 1200,placeopcodeslne,right$(hex$(pc),4)
text 1270,placeopcodeslne,right$(hex$(op_byte),2)
text 1460,placeopcodeslne,"NOP"
endif
endif

// Do nothing!

if execute=true

; no flags affected
fs = fs
fz = fz
f5 = f5
fh = fh
f3 = f3
fpv = fpv
fn = fn
fc = fc
exeTstates = 4

endif

return ;done


op_1:  // LD BC,nn

op$="LD BC,"
nxtpc=3

if monitormode=true
address=pcptr+pc
lsb=peekbyte(pcptr+pc+1)
msb=peekbyte(pcptr+pc+2)
num=msb*256+lsb

if hex_or_dec = false
// Decimal representation
text 1200,placeopcodeslne,digits$(pc,5)
text 1270,placeopcodeslne,digits$(op_byte,3)
text 1320,placeopcodeslne,digits$(lsb,3)
text 1370,placeopcodeslne,digits$(msb,3)
text 1460,placeopcodeslne,"LD BC , "+digits$(num,5)
else
// Hex representation
text 1200,placeopcodeslne,right$(hex$(pc),4)
text 1270,placeopcodeslne,right$(hex$(op_byte),2)
text 1320,placeopcodeslne,right$(hex$(lsb),2)
text 1370,placeopcodeslne,right$(hex$(msb),2)
text 1460,placeopcodeslne,"LD BC , "+right$(hex$(num),4)
endif
endif

if execute=true

lsb=peekbyte(savepc+1)
msb=peekbyte(savepc+2)
regc=lsb
regb=msb

; no flags affected
fs = fs
fz = fz
f5 = f5 ; Not used
fh = fh
f3 = f3 ; Not used
fpv = fpv
fn = fn
fc = fc

exeTstates = 10
endif
return ; DONE


op_2:  // LD (BC),A

nxt_pc=1

if monitormode=true

if hex_or_dec = false
// Decimal representation
text 1200,placeopcodeslne,digits$(pc,5)
text 1270,placeopcodeslne,digits$(op_byte,3)
text 1460,placeopcodeslne,"LD ( BC ) , A"+digits$(num,5)
else
// Hex representation
text 1200,placeopcodeslne,right$(hex$(pc),4)
text 1270,placeopcodeslne,right$(hex$(op_byte),2)
text 1460,placeopcodeslne,"LD ( BC ) , A"+right$(hex$(num),4)
endif
endif

if execute=true
; memorybank positon bc will be loaded with the value of a
; we could have array postion (b*256)+c = a but i think banks are needed for speed
rega=(regb*256)+regc  ; a will loaded in to memory location poke bc,a

; no flags affected
fs = fs
fz = fz
f5 = f5
fh = fh
f3 = f3
fpv = fpv
fn = fn
fc = fc

endif
exeTstates = 7
return ;done
This is very fast compared to the Select/Case Block! It's not really a decsion but a jump on which Byte/Opcode i have. But i don't have a diddly squat how to program/Code this in BlitZMax  Just the use of Select/Case.

Kind Regards Baggey

[TomToad]

Functions in BlitzMax are first-class functions.  That means a function can be treated the same as an object.  Stored in arrays and lists, and passed into and from other functions.

So you define a function in the normal way

Code: BlitzMax

1. Function MyFunc:int(a:int, b:int)
2.     DoStuff()
3. End Function

Then you can store a pointer to the function in another variable

Code: BlitzMax

1. Local AltFunc:Int(a:int, b:int) = MyFunc

Now you can call either result = MyFunc(10,20) or result = AltFunc(10,20), they both call the same function

So now you can write a function for each of your opcodes and place each function into an array

Code: BlitzMax

1. 'define the functions
2. Function Op0:Int()
3.     'put code here
4. End Function
5.  
6. Function Op1:Int()
7.     'put code here
8. End function
9.  
10. 'define more functions
11.  
12. Local FuncArray:Int()[256] 'create the array
13. 'assign the functions to the array elements
14. FuncArray[0] = Op0
15. FuncArray[1] = Op1
16. 'fill the rest of the array
17.  
18. 'get next opcode
19. opcode = GetNextOpcode()
20. 'call the proper function
21. FuncArray[opcode]()
22.  

Takes a bit more typing than with select/case, but works faster.

[Baggey]

Thanks guy's, Something to try speeding up my emulation 

Kind Regards Baggey

[TomToad]

Don't know if this would be of any use to you, but javidx9 on YouTube has videos on how to make a NES emulator.  He is using C++ and his own graphics engine, but most of the techniques he uses translates to BlitzMax.

https://youtube.com/playlist?list=PLrOv9FMX8xJHqMvSGB_9G9nZZ_4IgteYf

[Baggey]

He is using C++

Proably should be put some where else. But i use Blitzmax 1.5. The reason im using Blitzmax 1.5 is you install it and use it  Tried many other languages but when you start using librarys, Sdll's and linking to Modules and Make files and other stuff ive even forgot about. That needs to be there and then it dosent work! You kind of give up on them.

Oh well, getting old and set in my ways. 

Its like buying a car but before you can use it you need to get some wheels, get some breaks, get some tyres an engine, but do i need petrol or diesel? 

Kind Regards Baggey

[Baggey]

Takes a bit more typing than with select/case, but works faster.

So had a little play with the code and thought id be crafty to safe sometime typing and use a "for and next loop" for defining the function pointers.

Code: [Select]

' OO Opcodes

SuperStrict

'Import "Z80.bmx"

' Create OO opcodes Array

Local OO:Byte()[256] ' Create OO opcodes Array

' Assign the Functions into the Array elements Individualy
'OO[0] = OOO
        'OO[1] = OO1
'OO[2] = OO2

' Or

' As A big Line
'///Local OO:Byte()[]=[OOO,OO1,OO2]

' Or Automate the decleration process
' However the array pointers dont appear to be byte, short, int, string !!!????

For Local x:Byte = 0 To 2
Local text:String="OOO"
text$=text$+String.fromint(x)
text$= Right$(text$,3)
OO[x] = text
Next


 KeyDown(key_space)
Print
Print "OO Opcodes"
Print
' Call Opcode 0
OO[0]
' Call Opcode 2
OO[2]
' Call Opcode 1
OO[1]
Print
Print "Press SPACE to EXIT"

Repeat Until KeyDown(key_space)


Function OOO:Byte()' NOP
Print "0 ... NOP"
End Function

Function OO1:Byte()' LD BC,nn
 Print "1 ... LD BC,nn"
End Function

Function OO2:Byte()' LD (BC),A
 Print "2 ... LD (BC),A"
End Function

But the decleration dosent seem to be in any form of data format how would this be done ar can't it? 

Oh, How do i paste code in a BlitMax style window?

Kind Regards Baggey

[Steve Elliott]

Its like buying a car but before you can use it you need to get some wheels, get some breaks, get some tyres an engine, but do i need petrol or diesel? 

I agree.  There was a discussion here about Python and the same problem.   

[Derron]

blitzmax style {code=Blitzmax}your code{/code}. Replace curly brackets with square brackets.


Regarding your problem: Multiple variants possible:

Have a codegenerator.bmx which just outputs the "code" you then place in your main.bmx file. So no direct usage.

Code: BlitzMax

1. For local i:int = 0 to 255
2.   print "myarr["+i+"] = func"+(RSet(i, 3).Replace(" ", "0"))
3. Next
4.  

-> copy the output code, place the block of code in your file, done



Or you rely on "reflection" - as it might have trouble to find global functions, you store all your functios in eg a type "TOpCodes".
Then during start/initialization of your app (as it is slower than the raw array-access TomToad wrote about - but during startup the additional 1ms or so can be neglected).
So during start you do:

Code: BlitzMax

1. SuperStrict
2. Framework Brl.StandardIO
3. Import Brl.Reflection
4. Import Brl.Retro 'for RSet()
5.  
6.  
7. Type TOpCodes
8.   Function Func000:Int(); Print "000"; End Function
9.   Function Func001:Int(); Print "001"; End Function
10. End Type
11.  
12. Local opCodeFunctions:Int()[255]
13.  
14. Local t:TTypeId = TTypeId.ForName("TOpCodes") 'find the type by name, not a given type instance
15. If Not t Then Throw "Did you rename your TOpCodes?"
16. Local f:TFunction
17. For Local i:Int = 0 To 255
18.   f = t.FindFunction("Func" + (RSet(i, 3).Replace(" ", "0")))
19.   If f Then opCodeFunctions[i] = f.FunctionPtr()
20. Next
21.  
22.  
23. 'test execute
24. opCodeFunctions[1]()
25.  

You could also enhance the code to find a function like "FuncUnsupportedOpcode" which gets assigned if "f = null" ... so any opcode you use in the code - but somehow did not define in the type results in a throw/print/... message.


bye
Ron

[TomToad]

Your function names cannot start with a number, they must start with a letter or underscore.  So you can have Function Op001() or Function _001(), but not Function 001().

[Baggey]

Your function names cannot start with a number, they must start with a letter or underscore.  So you can have Function Op001() or Function _001(), but not Function 001().

Hi, Tom its a Capital O dont need the _ then.

DAMM it works until 100     Oh WELL Seemed eaisier to read rather than "_1OO" or "O1OO" Supouse now it's what one prefer's?

Kind Regards Baggey

[Baggey]

Hi Derron thanks for the code tip.

Ive rewritten it:-

Code: BlitzMax

1. ' Make a command line string for cutting and pasting
2.  
3.         Local text:String=""
4.         Local LongtextString:String=""
5.        
6.         For Local i:Int = 0 To 255
7.        
8.                 text=(RSet(i, 3).Replace("0", "O"))
9.                 text=text.Replace(" ", "O")
10.                 If i<255 Then text=text+"," Else text=text+"]"
11.                 LongTextString=LongTextString+text
12.        
13.         Next
14.        
15.         ' Note for some reason a )[ together throw a newline in printing out the string?
16.        
17.         text="Global OO:Byte()[]=["
18.         text=text+LongTextString
19.        
20.         Print text

Nice little trick that saved me loads of time on typing! but ive had to learn some more commands in BlitzMax to spit this text line out .LOL. 

Thanks All for the ideas. Now to get typing.

Kind Regards Baggey

[Derron]

text=(RSet(i, 3).Replace("0", "O"))
text=text.Replace(" ", "O")


I am quite sure that this does NOT create what you want it to create.

i = 0
text = Rset("0", 3) 'text="  0"
text = text.Replace("0", "O") 'text="  O"
text = text.Replace(" ", "O") 'text="OOO"

i = 1
text = Rset("1", 3) 'text="  1"
text = text.Replace("0", "O") 'text="  1"
text = text.Replace(" ", "O") 'text="OO1"


I assume you want to a structure like "O+number" and number having leading zeros?
If so - then copy my code and just prepend the "O"
text = "O" + (RSet(i, 3).Replace(" ", "0"))

i = 0
text = "O" + (RSet("0", 3).Replace(" ", "0")) 'O000

i = 1
text = "O" + (RSet("1", 3).Replace(" ", "0")) 'O001


PS: The Reflection code should be versatile enough too - for this case here. It is only executed on startup (so not each cycle) and always contains all functions you have defined - no "accidentally forgetting to recreate the copy-paste code".
But ... do as you prefer and what seems the "most easiest/versatile" approach (to you).


bye
Ron

[Baggey]

Thankyou again, as Tom pointed out you've got to use "_100" I found out when i got to 100. It dosent like the number Thats in front, thats why i used Capitol "O"

So after the tips heres my code for banging out the Template for OO_Opcodes 0 to 255 as Array Function pointers

Note, for some reason a )[ together throw a newline carrige return! in printing out the string? in the OUTPUT window Maybe a BUG?

Code: BlitzMax

1. ' Make a command line string for cutting and pasting
2.  
3.         Local text:String=""
4.         Local LongtextString:String=""
5.         Local i:Int=0
6.        
7.         Print
8.        
9.         For i = 0 To 255
10.        
11.                 text=(RSet(i, 3).Replace(" ", "0"))
12.                 If i<255 Then text="_"+text+"," Else text="_"+text+"]"
13.                 LongTextString=LongTextString+text
14.        
15.         Next
16.        
17.         ' Note for some reason a )[ together throw a newline carrige return! in printing out the string?
18.        
19.         text="Global OO:Byte(_[]=["
20.         text=text+LongTextString
21.        
22.         Print text
23.        
24. '       Now For the Function part
25.  
26.         For i = 0 To 255
27.        
28.                 text=(RSet(i, 3).Replace(" ", "0"))
29.                
30.                 Print
31.                 LongTextString="  Function _"+text+":Byte()' Opcode here"
32.                 Print LongTextString
33.                 Print "'"
34.                 Print "  End Function"
35.                
36.         Next
37.  

Wow what a lot of typing that saves. Now i need to reflect on Reflection  I Assume this is to pass variables into my Functions Id like to pass one byte in!
For now i could cheat with a Global variable thats seen by each Function. But i like the style of passing variables in.

Thankyou everyone who's helping me learn Blitzmax. It indeed is a nice language.

Kind Regards Baggey

[Derron]

text=(RSet(i, 3).Replace(" ", "0"))
If i<255 Then text="_"+text+"," Else text="_"+text+"]"
LongTextString=LongTextString+text


Could also be written as
LongTextString :+ "_" + (RSet(i, 3).Replace(" ", "0"))
If i = 255 Then LongTextString :+ "]"

(just wrote it to make you aware of ":+" to skip "text = text + x")


Regarding "passing bytes" .. you could have your functions accept a parameter?
function _000(param:int)

via reflection you can also pass parameters - but it is quite slow. So best is to have all the functions accept the same parameters (could be ":object" if passing type instances or strings)


bye
Ron