Rewriting with Heaviside function

### 10.1.8 Rewriting with Heaviside function

The linstep command rewrites piecewise defined expressions, as well as expressions involving step functions (signum and Heaviside) and/or absolute values, as a linear combination of Heaviside functions of linear arguments (see Section 8.3.2).

- linstep takes one mandatory argument and one optional argument:
  - expr, an expression.
  - Optionally, x, a variable (by default, x=x).
- linstep(expr ⟨,x ⟩) returns expr written as a sum of terms in form f(x)θ(x−a), where θ denotes Heaviside function.