Hi
I have been playing with fractint's own formula parser for some time and have noticed what I would call a bug in the parsing of the ident function.
Here's the two formulae that I have been using for testing purposes:
simon0063-A {
; Trying to figure out ident
;
z = p = pixel:
z = fn1(z * z) + p
|z| < 4
}
simon0063-B {
; Trying to figure out ident
;
z = p = pixel:
t = z * z
z = fn1(t) + p
|z| < 4
}
What the formula parser does is asks the user which function they wish to use. The only difference between formula 63-A and 63-B is the use of a temporary variable t to hold the result of the squaring of z and to pass that to the formula. If I select the function ident (which stands for identical), whatever is passed to the formula is what should be returned, but here's the resulting picture of each formula:
formula 63-A:
formula 63-B:
As you can see, 63-B shows the standard mandelbrot as you would expect, but 63-A shows something completely different. It is as if the multiplication is being completely ignored (and one instance of z is returned by the function).
I've tried this in the dos based 20.0 version via dosbox and both types of formula show the mandelbrot image correctly.
Shame I've only just noticed this as I was running a batch file creating lots of images (as per one of my previous posts) and had the original style of syntax in the formula for that (which means that every permutation where the formula used the ident function has generated an incorrect picture).
Simon
September 27, 2010, 10:33:21 PM
Does anyone know how to SIMPLY get 16-bit fractint DOS to go on Windows 7?
FractInt
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