Thank you Bruin and Kcrisman, for your attention.
The following codes are examples of the problem:
# fg denotes the convolution product f*g. The expected result is f*g = 0,
if t < 1 and f*g = t^2/2-t+1/2, if t > 1.
# For 0 < t < 1, it runs ok:
var('x,t')
assume(0<t,t<1)
f=unit_step(t-1)
g=t
fg = integrate(f(t=x)*g(t=t-x),x,0,t).simplify_full().expand()
show(fg)
forget()
#But, for t>1, there is a RuntimeError: mismatch in sr-to-maxima
var('x,t')
assume(1<t)
f=unit_step(t-1)
g=t
fg = integrate(f(t=x)*g(t=t-x),x,0,t).simplify_full().expand()
show(fg)
forget()
#In previous versions of Sage the answer, in the case piecewise functions
like f*g, could employ the functions like sign() or abs(), but no
Error messages appeared
#The following alternative raises no Error, but does not evaluate the f*g
function to t^2/2-t+1/2, as desired:
var('x,t')
assume(1<t)
f=unit_step(t-1)
g=t
fg = integrate(f(t=x)*g(t=t-x),x,0,t,hold=False)
show(fg)
forget()
Thank you again.
>>
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