If you think about it negative exponents require a completely different algorithm that is discontinuous with the one for positives. Instead of multiplying you divide n times.
You can take advantage of b^-n = 1/b^n Use a [moses] and two [pow], where the negative branch then has its reciprocal, or use [abs] and [sgn] to flip the negative ones through a reciprocal. cheers, Andy On Mon, Apr 22, 2013 at 03:07:43PM +0100, Joe White wrote: > > > > > Is this a known limitation or bug? > > it's most likely a feature that tries to protect you from things like: > > [-1( > > | > > [pow 0.5] > > | > > > Ahh yeah makes sense. > > I'm not sure why but I always feel uneasy using [expr], maybe because of > libpd :) > > [expr] does handle (-1)^0.5 with a NaN output though. Would it be possible > to add this to [pow] as well? Something like for negative base values, > non-integer exponent values would return NaN? > > Additionally for [pow] to output '0' seems wrong, because that is > definitely not the answer. I've never seen NaN output elsewhere so I'm > assuming [expr] outputs a symbol and not some Pd defined NaN type (maybe?). > > Thanks for the reply IOhannes! > > Cheers, > Joe > > On 22 April 2013 13:30, IOhannes m zmoelnig <zmoel...@iem.at> wrote: > > > -----BEGIN PGP SIGNED MESSAGE----- > > Hash: SHA1 > > > > On 2013-04-22 14:19, Joe White wrote: > > > Hi, > > > > > > Just realised putting a negative number into the [pow] object > > > outputs '0'?!? > > > > > > For example if I do: > > > > > > [-1 ( | [pow 2] > > > > > > it returns 0, where I would expect it to return 1. > > > > > > Is this a known limitation or bug? > > > > it's most likely a feature that tries to protect you from things like: > > > > [-1( > > | > > [pow 0.5] > > | > > > > > Are there any work arounds if I want a variable power? > > > > urgh, i had hoped to never have to tell people to use [expr], but > > there you go: > > > > [-1\ > > | > > [pack 0 2] > > | > > [expr pow($f1, $f2)] > > | > > [1\ > > > > vbmdf > > IOhannes > > -----BEGIN PGP SIGNATURE----- > > Version: GnuPG v1.4.12 (GNU/Linux) > > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ > > > > iEYEARECAAYFAlF1LW8ACgkQkX2Xpv6ydvRWDgCffaIHH1qXGqFYLlt1iiJQFW5Q > > OdEAnR8WVw+zxRKd8LWjVo95daJ/Aq6Y > > =PbB6 > > -----END PGP SIGNATURE----- > > > > _______________________________________________ > > Pd-list@iem.at mailing list > > UNSUBSCRIBE and account-management -> > > http://lists.puredata.info/listinfo/pd-list > > > _______________________________________________ > Pd-list@iem.at mailing list > UNSUBSCRIBE and account-management -> > http://lists.puredata.info/listinfo/pd-list _______________________________________________ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list