Wish C / Java style bitwise operators

wonder

wonder

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Can we have it the "old-school" way (| & ^ >> << ~)?

Take for example this expression:
B4X: 
int rgb = ((r & 0x0ff) << 16) | ((g & 0x0ff) << 8) | (b & 0x0ff);

The B4X equivalent is terribly long:
B4X: 
Dim rgb = Bit.Or(Bit.Or(Bit.ShiftLeft(Bit.And(r, 0x0ff), 16), Bit.ShiftLeft(Bit.And(g, 0x0ff), 8)), Bit.And(b, 0x0ff)) As Int
I'm not even sure if I got it right, such is the reduced readability... :(

Can we do something about it? :)
Many thanks in advance!

PS: It would be nice to have, at least, a parser. Something like this:
B4X: 
Dim rgb = Bit.ParseString("((r & 0x0ff) << 16) | ((g & 0x0ff) << 8) | (b & 0x0ff)") As Int
 
Last edited:
ggpanta

ggpanta

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I have had the same issue numerous times, the B4A notation is making simple expressions really convoluted, and unreadable. I wish the standard C notation was implemented since most other languages follow it.

Try to write this in B4A please and you will understand:
int binary = ((hash[offset] & 0x7f) << 24) | ((hash[offset + 1] & 0xff) << 16) | ((hash[offset + 2] & 0xff) << 8) | (hash[offset + 3] & 0xff);
 
stanmiller

stanmiller

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Like this?
B4X: 
Dim cb as Codeblock
cb.Compile("{|r,g,b|((r & 0x0ff) << 16) | ((g & 0x0ff) << 8) | (b & 0x0ff)}")
rgb1 = cb.Eval2( Array( 96, 53, 36 ) )
rgb2 = cb.Eval2( Array( 36, 37, 96 ) )
 

stanmiller

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It's from our soon to be released MTEEVAL library (w/ full source).



MTEEVAL implements a stack based expression compiler. Modifying the source you can support any expression your project needs like the hypothetical bitwise op example above.
 

stanmiller

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I'm working on the decompiler as we speak, but we should have the library posted later today. Source code will be maintained here:

https://github.com/macthomasengineering/mteeval-b4x-library

Currently the compiler supports basic math operators +-*/ but you could add bit shifting without too much drama.

You would tuck it in around here.



And then add the instructions to the machine.

 
Last edited:

stanmiller

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wonder said:
How do you get stuff compiled into machine code with B4A?
Click to expand...

When you own the CPU, anything is possible.



Decompiler is done too.



I'm meeting a client soon. When I get back, I'll package all this up and post the library and source.
 

wonder

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Wow!! So did you use B4A to create a virtual machine that runs on the Dalvik virtual machine, which in turn, can also run in my Android virtual machine on my real x86 machine PC????



I can't wait to give it a test drive!!
 

wonder

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@Erel, will you take this request into consideration? Using Bit.Something() is fine for simple operations, but when you need to read "a few" bits and combine "a few" bytes, it becomes a nightmare, in terms of readability.
 

wonder

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Thank you!
I'm not asking for a replacement, only for an alternative syntax... This way, I believe beginners and experts would be both happy.

Regarding the "&" operator, hopefully it can be segregated into bitwise or string concatenation, depending on context, something like:
If betweenStrings or betweenChars Then IsConcatenator = TRUE
 
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