Fold IVar into Param

Author: HarrisonGrodin

README.md

@@ -21,14 +21,14 @@ to manipulate.
 ### Example: ODE
 
 Let's build an ODE. First we define some variables. In a differential equation
-system, we need to differentiate between our unknown (dependent) variables, independent
-variables, and parameters. Therefore we label them as follows:
+system, we need to differentiate between our unknown (dependent) variables
+and parameters. Therefore we label them as follows:
 
 ```julia
 using ModelingToolkit
 
 # Define some variables
-@IVar t
+@Param t
 @Unknown x(t) y(t) z(t)
 @Deriv D'~t
 @Param σ ρ β
@@ -259,7 +259,7 @@ is accessible via a function-based interface. This means that all macros are
 syntactic sugar in some form. For example, the variable construction:
 
 ```julia
-@IVar t
+@Param t
 @Unknown x(t) y(t) z(t)
 @Deriv D'~t
 @Param σ ρ β
@@ -268,7 +268,7 @@ syntactic sugar in some form. For example, the variable construction:
 is syntactic sugar for:
 
 ```julia
-t = IndependentVariable(:t)
+t = Parameter(:t)
 x = Unknown(:x, dependents = [t])
 y = Unknown(:y, dependents = [t])
 z = Unknown(:z, dependents = [t])

src/equations.jl

@@ -14,6 +14,7 @@ Base.:~(lhs::Number    , rhs::Expression) = Equation(lhs, rhs)
 
 _is_derivative(x::Variable) = x.diff !== nothing
 _is_dependent(x::Variable) = x.subtype === :Unknown && !isempty(x.dependents)
+_is_parameter(ivs) = x -> x.subtype === :Parameter && x ∉ ivs
 _subtype(subtype::Symbol) = x -> x.subtype === subtype
 
 function extract_elements(eqs, predicates)

src/systems/diffeqs/diffeqsystem.jl

@@ -9,13 +9,15 @@ end
 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(:Parameter)]
-    _, ivs, dvs, ps = extract_elements(eqs, predicates)
+    predicates = [_is_derivative, _is_dependent]
+    _, dvs = extract_elements(eqs, predicates)
+    ivs = unique(vcat((dv.dependents for dv ∈ dvs)...))
+    ps, = extract_elements(eqs, [_is_parameter(ivs)])
     DiffEqSystem(eqs, ivs, dvs, ps, Matrix{Expression}(undef,0,0))
 end
 
 function DiffEqSystem(eqs, ivs)
-    predicates = [_is_derivative, _is_dependent, _subtype(:Parameter)]
+    predicates = [_is_derivative, _is_dependent, _is_parameter(ivs)]
     _, dvs, ps = extract_elements(eqs, predicates)
     DiffEqSystem(eqs, ivs, dvs, ps, Matrix{Expression}(undef,0,0))
 end

src/variables.jl

@@ -9,11 +9,9 @@ Variable(name; subtype::Symbol, dependents::Vector{Variable} = Variable[]) =
     Variable(name, subtype, nothing, dependents)
 
 Parameter(name,args...;kwargs...) = Variable(name,args...;subtype=:Parameter,kwargs...)
-IndependentVariable(name,args...;kwargs...) = Variable(name,args...;subtype=:IndependentVariable,kwargs...)
 Unknown(name,args...;kwargs...) = Variable(name,args...;subtype=:Unknown,kwargs...)
 
-export Variable,Parameter,Constant,Unknown,IndependentVariable,
-       @Param, @Const, @Unknown, @IVar
+export Variable, Parameter, Constant, Unknown, @Param, @Const, @Unknown
 
 
 Base.copy(x::Variable) = Variable(x.name, x.subtype, x.diff, x.dependents)
@@ -83,7 +81,7 @@ function _parse_vars(macroname, fun, x)
     return ex
 end
 
-for funs in [(:Unknown, :Unknown), (:IVar, :IndependentVariable), (:Param, :Parameter)]
+for funs in [(:Unknown, :Unknown), (:Param, :Parameter)]
     @eval begin
         macro ($(funs[1]))(x...)
             esc(_parse_vars(String($funs[1]), $funs[2], x))

test/ambiguity.jl

@@ -1,7 +1,7 @@
 using ModelingToolkit
 using Test
 
-@IVar t
+@Param t
 @Unknown x(t) y(t) z(t)
 
 struct __MyType__ end

test/basic_variables_and_operations.jl

@@ -1,7 +1,7 @@
 using ModelingToolkit
 using Test
 
-@IVar t
+@Param t
 @Unknown x(t) y(t) z(t)
 
 @Deriv D'~t # Default of first derivative, Derivative(t,1)

test/components.jl

@@ -22,7 +22,7 @@ function Lorenz(t)
     Lorenz(x, y, z, σ, ρ, β, generate_lorenz_eqs(t, x, y, z, σ, ρ, β))
 end
 
-@IVar t
+@Param t
 lz1 = Lorenz(t)
 lz2 = Lorenz(t)
 lz1.x ~ lz2.x

test/derivatives.jl

@@ -2,7 +2,7 @@ using ModelingToolkit
 using Test
 
 # Derivatives
-@IVar t
+@Param t
 @Unknown x(t) y(t) z(t)
 @Param σ ρ β
 @Deriv D'~t

test/internal.jl

@@ -2,7 +2,7 @@ using ModelingToolkit
 using Test
 
 # `Expr`, `Number` -> `Operation`
-@IVar a
+@Param a
 @Param b
 @Unknown x(t) y()
 @test convert(Expression, 2) == 2

test/simplify.jl

@@ -1,7 +1,7 @@
 using ModelingToolkit
 using Test
 
-@IVar t
+@Param t
 @Unknown x(t) y(t) z(t)
 
 null_op = 0*t