integrate - integration by quadrature
computes :
/x1
[
x = I f(v)dv
]
/x0
The evaluation hopefully satisfies following claim for accuracy: abs(I-x)<= max(ea,er*abs(I)) where I stands for the exact value of the integral.
integrate('sin(x)','x',0,%pi)
integrate(['if x==0 then 1,';
'else sin(x)/x,end'],'x',0,%pi)