Implement == (and hash) for Element

So that e.g. `resistor(1000) == resistor(1000)`, which previously gave
`false`.

src/ACME.jl

@@ -1,4 +1,4 @@
-# Copyright 2015, 2016, 2017, 2018, 2019, 2020, 2021 Martin Holters
+# Copyright 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2023 Martin Holters
 # See accompanying license file.
 
 module ACME
@@ -97,6 +97,11 @@ struct Element
     end
 end
 
+Base.:(==)(e1::Element, e2::Element) =
+    all(f -> (getfield(e1, f) == getfield(e2, f))::Bool, fieldnames(Element))
+Base.hash(e::Element, h::UInt) =
+    foldl((h, f) -> hash(getfield(e, f), h)::UInt, fieldnames(Element); init=h)
+
 for (n,m) in Dict(:nb => :mv, :nx => :mx, :nq => :mq, :nu => :mu)
   @eval ($n)(e::Element) = size(e.$m, 2)
 end

test/runtests.jl

@@ -1,4 +1,4 @@
-# Copyright 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022 Martin Holters
+# Copyright 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023 Martin Holters
 # See accompanying license file.
 
 include("checklic.jl")
@@ -40,6 +40,16 @@ end
     @test !ACME.setlhs!(solver, zeros(3,3))
 end
 
+@testset "Element equality" begin
+    @test resistor(1e3) == resistor(1e3)
+    @test hash(resistor(1e3)) == hash(resistor(1e3))
+    @test resistor(1e3) != resistor(2.2e3)
+    @test resistor(1) != voltagesource(1)
+    @test bjt(:npn) == bjt(:npn)
+    @test hash(bjt(:npn)) == hash(bjt(:npn))
+    @test bjt(:npn) != bjt(:pnp)
+end
+
 @testset "simple circuits" begin
     @testset "empty circuit" begin
         circ = @circuit begin end