posted 10 August 2010 16:59            

On page 148, referring to the Sound 'Basic live Capture and Looping', I'm stuck on this:

"Play 'Basic live capture & looping' and describe the function of each of the VCS
widgets. Based on their behavior, see if you can decipher the meaning of the
expressions in Frequency, LoopStart, and LoopEnd. (HINT: In CapyTalk, sign
tells you whether a value is positive or negative. It equals -1 for negative num-
bers, 1 for positive numbers and 0 for the value 0."

Referring to the latter challenge I cannot find anything with 'sign' used in these parameters at all and so do not understand the hint.

Thanks

Andrew

posted 10 August 2010 17:14            

In this particular sound, a negative Length value is meant to reverse the looping element. One way to achieve that is by multiplying the playback Frequency by -1.

So while the absolute value of Length determines the LoopEnd point, the 'sign' value is -1, 0, or 1 and determines whether the sample playback is forward or backwards.

posted 11 August 2010 09:19            

default * (2 * ( 0.5 - (!Length le: 0)))

with no 'sign' to be seen in the expression. I think this is where my confusion comes from. Perhaps the Sound has been changed since the book?

Thanks

posted 11 August 2010 11:36            

To deconstruct this expression:

(!Length le: 0)

is 1 when !Length is 0 or negative and it is 0 when !Length is positive.

( 0.5 - (!Length le: 0))

For positive !Length is 0.5. And for 0 or negative !Length, it is -0.5

(2 * ( 0.5 - (!Length le: 0)))

For positive !Length is 1. And for 0 or negative !Length, it is -1.

As Keph was saying, you could get a similar result using a more compact expression:

default * !Length sign

except that, when !Length is 0, your Sample would go silent.

posted 11 August 2010 17:56            

Thanks