refactor: remove vars, vars!

Author: AayushSabharwal

src/utils.jl

@@ -426,90 +426,6 @@ function isvariable(x)
     hasmetadata(x, VariableSource) || iscall(x) && operation(x) === getindex && isvariable(arguments(x)[1])::Bool
 end
 
-"""
-    vars(x; op=Differential)
-
-Return a `Set` containing all variables in `x` that appear in
-
-  - differential equations if `op = Differential`
-
-Example:
-
-```
-t = ModelingToolkit.t_nounits
-@variables u(t) y(t)
-D  = Differential(t)
-v  = ModelingToolkit.vars(D(y) ~ u)
-v == Set([D(y), u])
-```
-"""
-function vars(exprs::SymbolicT; op = Differential)
-    iscall(exprs) ? vars([exprs]; op = op) : Set([exprs])
-end
-vars(exprs::Num; op = Differential) = vars(unwrap(exprs); op)
-vars(exprs::Symbolics.Arr; op = Differential) = vars(unwrap(exprs); op)
-function vars(exprs; op = Differential)
-    if hasmethod(iterate, Tuple{typeof(exprs)})
-        foldl((x, y) -> vars!(x, unwrap(y); op = op), exprs; init = Set())
-    else
-        vars!(Set(), unwrap(exprs); op)
-    end
-end
-vars(eq::Equation; op = Differential) = vars!(Set(), eq; op = op)
-function vars!(vars, eq::Equation; op = Differential)
-    (vars!(vars, eq.lhs; op = op); vars!(vars, eq.rhs; op = op); vars)
-end
-function vars!(vars, O::AbstractSystem; op = Differential)
-    for eq in equations(O)
-        vars!(vars, eq; op)
-    end
-    return vars
-end
-function vars!(vars, O; op = Differential)
-    if isvariable(O)
-        if iscall(O) && operation(O) === getindex && iscalledparameter(first(arguments(O)))
-            O = first(arguments(O))
-        end
-        if iscalledparameter(O)
-            f = getcalledparameter(O)
-            push!(vars, f)
-            for arg in arguments(O)
-                if symbolic_type(arg) == NotSymbolic() && arg isa AbstractArray
-                    for el in arg
-                        vars!(vars, unwrap(el); op)
-                    end
-                else
-                    vars!(vars, arg; op)
-                end
-            end
-            return vars
-        end
-        return push!(vars, O)
-    end
-    if symbolic_type(O) == NotSymbolic() && O isa AbstractArray
-        for arg in O
-            vars!(vars, unwrap(arg); op)
-        end
-        return vars
-    end
-    !iscall(O) && return vars
-
-    operation(O) isa op && return push!(vars, O)
-
-    if operation(O) === (getindex)
-        arr = first(arguments(O))
-        iscall(arr) && operation(arr) isa op && return push!(vars, O)
-        isvariable(arr) && return push!(vars, O)
-    end
-
-    isvariable(operation(O)) && push!(vars, O)
-    for arg in arguments(O)
-        vars!(vars, arg; op = op)
-    end
-
-    return vars
-end
-
 function collect_operator_variables(sys::AbstractSystem, args...)
     collect_operator_variables(equations(sys), args...)
 end