|
 |
> > #local Rotate = transform { rotate ... }
> > object { ... Rotate }
>
> I don't understand your answer at all.
Sorry, I was probably unclear -- in that I have omitten several steps that
seemed obvious to me... I'll try once again. Here is your code with my
marks:
if(z>0)
sphere{0 1
^-------- (A)
else
box{-1 1
^--------------(B)
end
rotate x* if ( vlength(<x,y,z> > 1 ) 30 else (2+x+y+z) end
} <-------------------(C)
If 'if' statement were a real statement, and not merely a pre-processor
directive, then you would be unable to place parentheses like that (marks
(A) and (B)). Such placement is always considered dangerous -- you are
subdividing statement into pieces, AND pre-processor is unable to help you
to find any bugs, since it has no notion of what is between its
directives... Even if you have exceptional abilities and can maintain such a
code, other readers of your code may easily get confused with such grouping
(well, not with *that* example, but with a bit more complex...) That is why
such (once again, not this, but a more complicated code written in the same
manner) is often called a "write-only" code.
You are not to blame for that -- since 'if', 'switch' etc. keywords are
pre-processor directives rather than true language statements (that obey
some syntax rules), you are almost encoraged to write like that.
Now the part that confused you... In a well-designed language, you may
almost always gain good performance, but -- without hacks. I tried to draw
an example... To me, it was obvious that what you tried to do (with if-end
block containing marks (A) and (B)) was to supply a single transform to
variable shape definition -- so I just tried to illustrate that, if you were
dealing with an interpreter, and not mere pre-processor, you would be
*forced* to define transformation and then re-use that in several object
definitions. The interpreter would *not* allow you break pairs of
parentheses like that. And guess what? I think that that would be right!
Post a reply to this message
|
|
