Replace prior :Variable with Julia variable assignment

Author: HarrisonGrodin

README.md

@@ -47,7 +47,7 @@ Each operation builds an `Operation` type, and thus `eqs` is an array of
 analyzed by other programs. We can turn this into a `DiffEqSystem` via:
 
 ```julia
-de = DiffEqSystem(eqs,[t],[x,y,z],Variable[],[σ,ρ,β])
+de = DiffEqSystem(eqs,[t],[x,y,z],[σ,ρ,β])
 de = DiffEqSystem(eqs)
 ```
 
@@ -285,10 +285,10 @@ D = Differential(t) # Default of first derivative, Derivative(t,1)
 The system building functions can handle intermediate calculations. For example,
 
 ```julia
-@Unknown a x y z
+@Unknown x y z
 @Param σ ρ β
-eqs = [a ~ y-x,
-       0 ~ σ*a,
+a = y - x
+eqs = [0 ~ σ*a,
        0 ~ x*(ρ-z)-y,
        0 ~ x*y - β*z]
 ns = NonlinearSystem(eqs,[x,y,z],[σ,ρ,β])

src/systems/diffeqs/diffeqsystem.jl

@@ -2,23 +2,22 @@ mutable struct DiffEqSystem <: AbstractSystem
     eqs::Vector{Equation}
     ivs::Vector{Variable}
     dvs::Vector{Variable}
-    vs::Vector{Variable}
     ps::Vector{Variable}
     jac::Matrix{Expression}
 end
 
-DiffEqSystem(eqs, ivs, dvs, vs, ps) = DiffEqSystem(eqs, ivs, dvs, vs, ps, Matrix{Expression}(undef,0,0))
+DiffEqSystem(eqs, ivs, dvs, ps) = DiffEqSystem(eqs, ivs, dvs, ps, Matrix{Expression}(undef,0,0))
 
 function DiffEqSystem(eqs)
-    predicates = [_is_derivative, _subtype(:IndependentVariable), _is_dependent, _subtype(:Unknown), _subtype(:Parameter)]
-    _, ivs, dvs, vs, ps = extract_elements(eqs, predicates)
-    DiffEqSystem(eqs, ivs, dvs, vs, ps, Matrix{Expression}(undef,0,0))
+    predicates = [_is_derivative, _subtype(:IndependentVariable), _is_dependent, _subtype(:Parameter)]
+    _, ivs, dvs, ps = extract_elements(eqs, predicates)
+    DiffEqSystem(eqs, ivs, dvs, ps, Matrix{Expression}(undef,0,0))
 end
 
 function DiffEqSystem(eqs, ivs)
-    predicates = [_is_derivative, _is_dependent, _subtype(:Unknown), _subtype(:Parameter)]
-    _, dvs, vs, ps = extract_elements(eqs, predicates)
-    DiffEqSystem(eqs, ivs, dvs, vs, ps, Matrix{Expression}(undef,0,0))
+    predicates = [_is_derivative, _is_dependent, _subtype(:Parameter)]
+    _, dvs, ps = extract_elements(eqs, predicates)
+    DiffEqSystem(eqs, ivs, dvs, ps, Matrix{Expression}(undef,0,0))
 end
 
 function generate_ode_function(sys::DiffEqSystem;version = ArrayFunction)

test/system_construction.jl

@@ -3,7 +3,7 @@ using Test
 
 # Define some variables
 @IVar t
-@Unknown x(t) y(t) z(t) a()
+@Unknown x(t) y(t) z(t)
 @Deriv D'~t # Default of first derivative, Derivative(t,1)
 @Param σ ρ β
 @Const c=0
@@ -12,7 +12,7 @@ using Test
 eqs = [D(x) ~ σ*(y-x),
        D(y) ~ x*(ρ-z)-y,
        D(z) ~ x*y - β*z]
-de = DiffEqSystem(eqs,[t],[x,y,z],Variable[],[σ,ρ,β])
+de = DiffEqSystem(eqs,[t],[x,y,z],[σ,ρ,β])
 ModelingToolkit.generate_ode_function(de)
 ModelingToolkit.generate_ode_function(de;version=ModelingToolkit.SArrayFunction)
 jac_expr = ModelingToolkit.generate_ode_jacobian(de)
@@ -24,7 +24,7 @@ ModelingToolkit.generate_ode_iW(de)
 de2 = DiffEqSystem(eqs, [t])
 
 function test_vars_extraction(de, de2)
-    for el in (:ivs, :dvs, :vs, :ps)
+    for el in (:ivs, :dvs, :ps)
         names2 = sort(collect(var.name for var in getfield(de2,el)))
         names = sort(collect(var.name for var in getfield(de,el)))
         @test names2 == names
@@ -61,11 +61,11 @@ end
 @test_broken test_eqs(de1.eqs, lowered_eqs)
 
 # Internal calculations
-eqs = [a ~ y-x,
-       D(x) ~ σ*a,
+a = y - x
+eqs = [D(x) ~ σ*a,
        D(y) ~ x*(ρ-z)-y,
        D(z) ~ x*y - β*z]
-de = DiffEqSystem(eqs,[t],[x,y,z],[a],[σ,ρ,β])
+de = DiffEqSystem(eqs,[t],[x,y,z],[σ,ρ,β])
 ModelingToolkit.generate_ode_function(de)
 jac = ModelingToolkit.calculate_jacobian(de)
 f = ODEFunction(de)
@@ -84,13 +84,12 @@ end
 
 ModelingToolkit.generate_nlsys_function(ns)
 
-@Unknown _x
 @Deriv D'~t
 @Param A B C
-eqs = [_x ~ y/C,
-       D(x) ~ -A*x,
+_x = y / C
+eqs = [D(x) ~ -A*x,
        D(y) ~ A*x - B*_x]
-de = DiffEqSystem(eqs,[t],[x,y],Variable[_x],[A,B,C])
+de = DiffEqSystem(eqs,[t],[x,y],[A,B,C])
 test_vars_extraction(de, DiffEqSystem(eqs,[t]))
 test_vars_extraction(de, DiffEqSystem(eqs))
 @test eval(ModelingToolkit.generate_ode_function(de))([0.0,0.0],[1.0,2.0],[1,2,3],0.0) ≈ -1/3