Hello, list. I hope that you're having a nice Sunday.
I have this function to approximate the dilogarithm function:
import("stdfaust.lib");
Li2(N, x) = ba.if( x < -1,
-1 * ma.PI ^ 2 / 6 - .5 * log(-x) ^ 2
- sum(i, N, 1 / ((i + 1) ^ 2 * x ^ (i + 1))),
ba.if( abs(x) <= 1,
sum(i, N, x ^ (i + 1) / (i + 1) ^ 2),
ma.PI ^ 2 / 3 - .5 * log(x) ^ 2
- sum(i, N, 1 / ((i + 1) ^ 2 * x ^ (i + 1
)))));
process = -2.0', -1.5', -1.0', -.5', -.1', .1', .5', 1.0', 1.5', 2.0' : par(
i, 10, Li2(50));
//process = -2', -1.5', -1.0', -.5', -.1', .1', .5', 1.0', 1.5', 2' :
par(i, 10, Li2(50));
I am calling it with delayed values to avoid division by zero or NaN in the
non-outputting branches.
I noticed that if I call it with int values as you can see in the commented
process, I get -inf for 2 and -2, whereas I get the correct values if I use
float.
Please try with:
faust2csvplot -double test_Li2.dsp
./test_Li2 -n 1 -s 1
I am aware that the arguments of some functions that use pattern matching
must be ints, but I was also convinced that all values in Faust are treated
as floats with math functions.
What is good practice for floats and ints? Should I explicitly always write
1.0 instead of 1 as if I'm writing C++?
Other than that, can you tell why -2 or 2 is producing -inf?
Thanks.
--
Dr Dario Sanfilippo
http://dariosanfilippo.com
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