Display returned integral containing assumptions with integral sign

Question

From solving the PDE example of the general 1 dim heat equation in Nasser Abbasi's site https://www.12000.org/my_notes/pde_in_CAS/maple_2019_and_mma_12/insu157.htm#x182-1810003.1.1 (his problem No 151) I get the described solution containing the integral

Integrate[f[x] Sin[(\[Pi] x n)/L], {x, 0, L}, Assumptions -> k > 0 && L > 0]

Instead of this output form, how can I display this integral with the integral sign, as it is displayed in Nasser's site, not showing the assumptions? Neither StandardForm nor TraditionalForm does this. Is taking out (e.g. manually) the assumptions from Integrate's arguments the only way? How can I have Mathematica output the solution with the integral displayed with the integral sign and without the assumptions? Can the assumptions (any assumptions) be taken out automatically from Integrate's arguments, e.g. by some kind of replacement? I can't find out what this general replacement rule would have to be.

Thanks for help!

Answer 1

Depending on your needs consider $PrePrint and MakeBoxes. Something like this:

MakeBoxes[
  Integrate[a__, Assumptions -> _],
  fmt : TraditionalForm
] := MakeBoxes[Integrate[a], fmt]

Now when you view the integral in TraditionalForm:

Integrate[f[x] Sin[(n π x)/L], {x, 0, L}, 
  Assumptions -> k > 0 && L > 0] // TraditionalForm

$$\int_0^L f(x) \sin \left(\frac{\pi n x}{L}\right) \, dx$$

And TeXForm works too because by default is uses TraditionalForm:

Integrate[f[x] Sin[(n π x)/L], {x, 0, L}, 
  Assumptions -> k > 0 && L > 0] // TeXForm

\int_0^L f(x) \sin \left(\frac{\pi  n x}{L}\right)\, dx