interpolation algorithm

[stryd_one]

what's wrong with a shift?

I didn't say there was anything wrong with a shift.

it's a native operation of the processor, therefore fast and there's a native operator in C?

That's correct.

maybe you could use a byte-address to do what you want?:

<snip>

All that work demonstrates that you've kinda missed my point - I expected the language to take care of this, without my interaction, without writing extra code, without messing around, etc. It doesn't. No problem! I just kinda assumed that it would be 'smarter' than it is.

[This N°9]

All that work demonstrates that you've kinda missed my point - I expected the language to take care of this, without my interaction, without writing extra code, without messing around, etc. It doesn't. No problem! I just kinda assumed that it would be 'smarter' than it is.

I think the target of C is to have a language that is more "human" than asm, but enough close to the machine to generate fast code. therefore too much overhead would not do it any good.

I expected the language to take care of this

how should the language "now" what you want to do if you don't tell it ?

but C++ is very powerfull, you could for example write your own operator, that gives you the msb of

an int as result. you can write operators like objects. I never did this, but I think this is a very powerfull

feature. you can even "overload" operators, e.g. if you want to simply add two strings with "+", you can

overload the "+" operator and write a routine to process the string-addition. all other types will be handled

still in the native manner. check it out..

I hope this input is usefull for you  ;)

[stryd_one]

I think the target of C is to have a language that is more "human" than asm, but enough close to

the machine to generate fast code. therefore too much overhead would not do it any good.

That's a good point. It's one of the things I have grown to like about C, is that it stays quite low-level, without needing me to do *all* of the thinking ;)

how should the language "now" what you want to do if you don't tell it ?

Magic, of course ;D Hehehe... well of course there are ways to handle it, but in the end, the way it is done makes sense.

but C++ is very powerfull<snip>

I hope this input is usefull for you  ;)

Yeh, thanks dude. I don't know squat about C++!

[This N°9]

I don't have so much experience with C, but during a period with no regular job, I read a book about the language, and made my notes like a proper student  ;D

so I can refer them now, thats very usefull. also I'am familar with the syntax from writing in PHP and JavaScript. There is still some stuff that confuses me, but what I like about C: it seems to be weird, but in the end it is very consequent.

[wackazong]

I did the interpolation algorithm in C, have a look at the code, should work. It interpolates in 33 steps, step can be 0 to 32.

/////////////////////////////////////////////////////////////////////////////
// Interpolate
/////////////////////////////////////////////////////////////////////////////
unsigned char KNOEPFLI_Interpolate32(unsigned char step, unsigned char value1, unsigned char value2)
{
	unsigned char swap, diff;

	//send out value2 if step is the max value
	if( step == 32 ) {
		return value2;
	};
	//send out value1 if step i 0
	if( step == 0 ) {
		return value1;
	};
	//invert the interpolation if value1 > value2
	if( value1 > value2 ) {
		//swap the values
		swap = value2;
		value2 = value1;
		value1 = swap;
		//--step because we are counting from 0 to 32, not to 31
		--step;
		//invert the step counter
		step = ~step;
		//clear the upper three bits
		step &= 0x1f;
	};

	//get the difference
	diff = value2 - value1;

	//divide it through the total number of steps (>>5) and multiply it with step (gives an integer) then get the high byte, 

	//shift the step counter three to the left to make it 8bit, store it in PRODL
	PRODL = step << 3;

	//store diff in PRODH
	PRODH = diff;  

	//do the multiplication in assembler
	__asm
    movf _PRODL, W
    mulwf _PRODH, 0
	__endasm;

	//add the lower value
	return value1 + PRODH;

}

[stryd_one]

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