Re: QwtCurve::drawSpline()

[Uwe R. <Uwe...@ep...>]

On Thursday 03 May 2001 17:16, Pieter van Beek wrote:
> Hello Group,
>
> While checking the code in QwtCurve I found out that operator& and
> operator| (binary AND and OR operations) are often used where I'd expect
> operator&& and operator|| (logical AND and OR operations).

Well, it saves some memory as you can save 8 boolean flags in one byte using 
the bits. (flag &1) checks the first bit, (flag & 4) f.e the 3. bit..
(flag |= 4) sets the 3 bit, (flag &= ~4) clears the 3 bit.

When you have a look at qwtcurve.h you will find 

	Auto = 0, Yfx = 1, Xfy = 2, Parametric = 4, Periodic = 8, Inverted = 16;

As you can see these are exactly the first 6 bits of a byte. Of course you 
could use bitfields as well, what is a lot easier to read, but the technique 
above survived somehow from early assembler and C programming and is in 
common use up to now.

HTH,
Uwe