Remove @var and :Variable subtype

Now represented as a zero-dependent DependentVariable.

Author: HarrisonGrodin

README.md

@@ -92,7 +92,7 @@ derivatives are zero. We could use dependent variables for our nonlinear system
 variables. Here we will show the latter. We write:
 
 ```julia
-@Var x y z
+@DVar x y z
 @Param σ ρ β
 
 # Define a nonlinear system
@@ -285,7 +285,7 @@ D = Differential(t) # Default of first derivative, Derivative(t,1)
 The system building functions can handle intermediate calculations. For example,
 
 ```julia
-@Var a x y z
+@DVar a x y z
 @Param σ ρ β
 eqs = [a ~ y-x,
        0 ~ σ*a,

src/systems/diffeqs/diffeqsystem.jl

@@ -101,7 +101,7 @@ function generate_ode_iW(sys::DiffEqSystem, simplify=true)
     diff_exprs = filter(!isintermediate, sys.eqs)
     jac = sys.jac
 
-    gam = Variable(:gam)
+    gam = DependentVariable(:gam)
 
     W = LinearAlgebra.I - gam*jac
     W = SMatrix{size(W,1),size(W,2)}(W)

src/systems/nonlinear/nonlinear_system.jl

@@ -7,20 +7,17 @@ struct NonlinearSystem <: AbstractSystem
 end
 
 function NonlinearSystem(eqs, vs, ps;
-                         v_name = :Variable,
-                         dv_name = :DependentVariable,
+                         v_name = :DependentVariable,
                          p_name = :Parameter)
-    NonlinearSystem(eqs, vs, ps, [v_name,dv_name], p_name)
+    NonlinearSystem(eqs, vs, ps, [v_name], p_name)
 end
 
 function NonlinearSystem(eqs;
-                         v_name = :Variable,
-                         dv_name = :DependentVariable,
+                         v_name = :DependentVariable,
                          p_name = :Parameter)
-    # Allow the use of :DependentVariable to make it seamless with DE use
-    targetmap = Dict(v_name => v_name, dv_name => v_name, p_name => p_name)
+    targetmap = Dict(v_name => v_name, p_name => p_name)
     vs, ps = extract_elements(eqs, targetmap)
-    NonlinearSystem(eqs, vs, ps, [v_name,dv_name], p_name)
+    NonlinearSystem(eqs, vs, ps, [v_name], p_name)
 end
 
 function generate_nlsys_function(sys::NonlinearSystem)

src/variables.jl

@@ -5,16 +5,15 @@ mutable struct Variable <: Expression
     dependents::Vector{Variable}
 end
 
-Variable(name; subtype::Symbol=:Variable, dependents::Vector{Variable} = Variable[]) =
+Variable(name; subtype::Symbol, dependents::Vector{Variable} = Variable[]) =
     Variable(name, subtype, nothing, dependents)
-Variable(name, args...; kwargs...) = Variable(name, args...; subtype=:Variable, kwargs...)
 
 Parameter(name,args...;kwargs...) = Variable(name,args...;subtype=:Parameter,kwargs...)
 IndependentVariable(name,args...;kwargs...) = Variable(name,args...;subtype=:IndependentVariable,kwargs...)
 DependentVariable(name,args...;kwargs...) = Variable(name,args...;subtype=:DependentVariable,kwargs...)
 
 export Variable,Parameter,Constant,DependentVariable,IndependentVariable,
-       @Var, @Param, @Const, @DVar, @IVar
+       @Param, @Const, @DVar, @IVar
 
 
 Base.copy(x::Variable) = Variable(x.name, x.subtype, x.diff, x.dependents)
@@ -68,7 +67,7 @@ function _parse_vars(macroname, fun, x)
         @assert iscall || issym "@$macroname expects a tuple of expressions!\nE.g. `@$macroname x y z`"
 
         if iscall
-            dependents = :([$(_var.args[2:end]...)])
+            dependents = :(Variable[$(_var.args[2:end]...)])
             lhs = _var.args[1]
         else
             dependents = Variable[]
@@ -84,9 +83,7 @@ function _parse_vars(macroname, fun, x)
     return ex
 end
 
-for funs in ((:DVar, :DependentVariable), (:IVar, :IndependentVariable),
-             (:Var, :Variable),
-             (:Param, :Parameter))
+for funs in [(:DVar, :DependentVariable), (:IVar, :IndependentVariable), (:Param, :Parameter)]
     @eval begin
         macro ($(funs[1]))(x...)
             esc(_parse_vars(String($funs[1]), $funs[2], x))

test/derivatives.jl

@@ -3,7 +3,7 @@ using Test
 
 # Derivatives
 @IVar t
-@Var x(t) y(t) z(t)
+@DVar x(t) y(t) z(t)
 @Param σ ρ β
 @Deriv D'~t
 dsin = D(sin(t))
@@ -43,5 +43,5 @@ jac = ModelingToolkit.calculate_jacobian(sys)
 @test jac[3,3] == -1*β
 
 # Variable dependence checking in differentiation
-@Var a(t) b(a)
+@DVar a(t) b(a)
 @test D(b) ≠ Constant(0)

test/internal.jl

@@ -4,8 +4,7 @@ using Test
 # `Expr`, `Number` -> `Operation`
 @IVar a
 @Param b
-@DVar x(t)
-@Var y
+@DVar x(t) y()
 @test convert(Expression, 2) == 2
 expr = :(-inv(2sqrt(+($a, $b))))
 op   = Operation(-, [Operation(inv,

test/system_construction.jl

@@ -3,11 +3,10 @@ using Test
 
 # Define some variables
 @IVar t
-@DVar x(t) y(t) z(t)
+@DVar x(t) y(t) z(t) a()
 @Deriv D'~t # Default of first derivative, Derivative(t,1)
 @Param σ ρ β
 @Const c=0
-@Var a
 
 # Define a differential equation
 eqs = [D(x) ~ σ*(y-x),
@@ -85,7 +84,7 @@ end
 
 ModelingToolkit.generate_nlsys_function(ns)
 
-@Var _x
+@DVar _x
 @Deriv D'~t
 @Param A B C
 eqs = [_x ~ y/C,
@@ -95,7 +94,7 @@ de = DiffEqSystem(eqs,[t],[x,y],Variable[_x],[A,B,C])
 @test eval(ModelingToolkit.generate_ode_function(de))([0.0,0.0],[1.0,2.0],[1,2,3],0.0) ≈ -1/3
 
 # Now nonlinear system with only variables
-@Var x y z
+@DVar x y z
 @Param σ ρ β
 
 # Define a nonlinear system

test/variable_parsing.jl

@@ -1,16 +1,6 @@
 using ModelingToolkit
 using Test
 
-@Var a b
-a1 = Variable(:a)
-@test a1 == a
-@test convert(Expr, a) == :a
-
-@Var begin
-    a
-    b
-end
-
 @IVar t
 @DVar x(t)
 @DVar y(t)