Symbolic tspan

[YingboMa]

We just need a tspan field in time dependent systems.

[Jay-sanjay]

@YingboMa Hello sir, would you please elaborate the issue more, I am really interested in it ?

[Spinachboul]

In this, can we add the tspan in the following application available:
https://github.com/SciML/ModelingToolkit.jl/blob/master/examples/electrical_components.jl