[Help-gsl] qags, qagp, and qawc

[Nicolas Bock]

Hello list,

I would like to integrate a function that's roughly of the form 1 / (x 
- x_0). The integration limits are a < x_0 < b.

I tried to integrate 1/(x - x_0) with different limits, a and b, with 
qags, qagp, and qawc. Only qawc produced the correct answer for 
different choices of a and b, whereas qags and qagp sometimes worked 
and sometimes didn't. From the description of qags and qagp it wasn't 
quite clear to me if that's something to be expected or not. Should 
qags and qagp be able to integrate this type of singularity?

In another test I tried the integral 1 / (x - x_0)^2 and found to my 
surprise that qawc does not produce the right answer this time. Is it 
not able to handle singularities of higher order?

Thanks already in advance,

                nick