I don't understand what is happening in the simple csd below:

During the init pass, gival is initialized to 0, but instr 2 changes it to 
2. Meanwhile, instr 1 correctly evaluates it to 0, falling into the if/then 
construction (print gival), the condition being true.

During the k passes, instr 1, consistently prints (printk) gival as = 2, as 
you'd expect - since instr 2 changed its value.

However, *it should never have fallen into the if/then construction*; as the 
condition is now false (gival == 2).

If the if/then construction is changed to if/goto, the same evaluation error 
occurs.

This, BTW, is all with the old parser, Windows XP, Csound 5.06. (And of 
course if instruments 1 and 2 are interchanged, all works as expected.)

What's going on?

Art Hunkins




-odac


sr = 44100
kr = 44100
nchnls = 1
gival init 0

instr 1

if gival != 2 then
print gival
printk .1, gival
endif
endin

instr 2
gival = 2
endin




i1 0 1
i2 0 1

e

 

The reason is this:

1) if ... then  is evaluated at i-time when gival == 0
Since the condition is true, both print statements will be executed. At this stage (initi-pass) only print is executed

2) instr 2 changes the value of gival to 2 at its init-pass

3) the printk statement now runs at performance time and correctly reads the global var value (now 2).

NB: if you start instr 1  1-kcycle after instr 2, nothing will print.

Victor
On 17 Feb 2012, at 20:54, Art Hunkins wrote:

> I don't understand what is happening in the simple csd below:
> 
> During the init pass, gival is initialized to 0, but instr 2 changes it to 2. Meanwhile, instr 1 correctly evaluates it to 0, falling into the if/then construction (print gival), the condition being true.
> 
> During the k passes, instr 1, consistently prints (printk) gival as = 2, as you'd expect - since instr 2 changed its value.
> 
> However, *it should never have fallen into the if/then construction*; as the condition is now false (gival == 2).
> 
> If the if/then construction is changed to if/goto, the same evaluation error occurs.
> 
> This, BTW, is all with the old parser, Windows XP, Csound 5.06. (And of course if instruments 1 and 2 are interchanged, all works as expected.)
> 
> What's going on?
> 
> Art Hunkins
> 
> 
> 
> 
> -odac
> 
> 
> sr = 44100
> kr = 44100
> nchnls = 1
> gival init 0
> 
> instr 1
> 
> if gival != 2 then
> print gival
> printk .1, gival
> endif
> endin
> 
> instr 2
> gival = 2
> endin
> 
> 
> 
> 
> i1 0 1
> i2 0 1
> 
> e
> 
>  
> 
> 
> Send bugs reports to the Sourceforge bug tracker
>           https://sourceforge.net/tracker/?group_id=81968&atid=564599
> Discussions of bugs and features can be posted here
> To unsubscribe, send email sympa@lists.bath.ac.uk with body "unsubscribe csound"
> 

Dr Victor Lazzarini
Senior Lecturer
Dept. of Music
NUI Maynooth Ireland
tel.: +353 1 708 3545
Victor dot Lazzarini AT nuim dot ie