simpler example?

[robbiemu]

hate to ask something stupid but, how do I use this to solve for h in
4 + 2 * h - 3 / 4 = 32 - 2 * 5

this is the sort of thing that I figured would be a primary typical hello-world example, but the documentation makes it looks like I must supply h and let expression = equation.parse::<Expression>().unwrap(); from the example panics

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: [Simple { span: 19..20, reason: Unexpected, 
expected: {Some('=')}, found: Some(' '), label: None }]'

[robbiemu]

in python's sympy, I would do about this:

>>> from sympy import sympify, solve, Eq, symbols
>>> def solve_equation(equation_str, variable='h'):
...     var = symbols(variable)
...     lhs_str, rhs_str = equation_str.split('=')
...     lhs_expr = sympify(lhs_str)
...     rhs_expr = sympify(rhs_str)
...     equation = Eq(lhs_expr, rhs_expr)
...     solutions = solve(equation, var)
...     return solutions
>>> equation_str = "4 + 2 * h - 3 / 4 = 32 - 2 * 5"
>>> solve_equation(equation_str)
[75/8]

I tried:

    let (lhs_eq, rhs_eq) = equation.split_once(" = ").unwrap();
    let lhs = lhs_eq.parse::<Expression>().unwrap();
    let rhs = rhs_eq.parse::<Expression>().unwrap();
    let expression = eq(lhs, rhs);

    dbg!(&expression)

    let mut context = HashMap::new();
    context.insert("h".to_string(), int(1));
    let value = match expression.evaluate(context) {
      Ok(n) => Some(n.to_string().parse().unwrap()),
      _ => None,
    };

but it looks like I have to manually refactor the equation to remove the variable.

&expression = Equal(
    Quotient(
        Sum(
            Integer(
                4,
            ),
            Product(
                Integer(
                    2,
                ),
                Difference(
                    Variable(
                        "h",
                    ),
                    Integer(
                        3,
                    ),
                ),
            ),
        ),
        Integer(
            4,
        ),
    ),
    Product(
        Difference(
            Integer(
                32,
            ),
            Integer(
                2,
            ),
        ),
        Integer(
            5,
        ),
    ),
)
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: ParseIntError { kind: InvalidDigit }', src/part2_solver.rs:64:43