Merge pull request #1247 from hersle/dual_num_isequal

Resolve isequal(Num, ForwardDiff.Dual) ambiguity
JuliaSymbolics · Aug 29, 2024 · db877fb · db877fb
2 parents c91be2e + f0bcc47
commit db877fb
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diff --git a/ext/SymbolicsForwardDiffExt.jl b/ext/SymbolicsForwardDiffExt.jl
@@ -103,6 +103,25 @@ function binary_dual_definition(M, f, Ts)
     return expr
 end
 
+#####################
+# Generic Functions #
+#####################
+
+# Predicates #
+#------------#
+
+for pred in [:isequal, :(==)]
+    @eval begin
+        @define_binary_dual_op(
+            Base.$(pred),
+            $(pred)(value(x), value(y)) && $(pred)(partials(x), partials(y)),
+            $(pred)(value(x), y)        && iszero(partials(x)),
+            $(pred)(x, value(y))        && iszero(partials(y)),
+            $AMBIGUOUS_TYPES
+        )
+    end
+end
+
 ###################################
 # General Mathematical Operations #
 ###################################

diff --git a/test/forwarddiff_symbolic_dual_ops.jl b/test/forwarddiff_symbolic_dual_ops.jl
@@ -107,3 +107,10 @@ for f ∈ (hypot, muladd)
 end
 
 # fma is not defined for Symbolics.Num
+
+# https://github.com/JuliaSymbolics/Symbolics.jl/issues/1246
+@testset "isequal type ambiguity" begin
+    @variables z
+    y(x) = isequal(z, x) ? 0 : x
+    @test ForwardDiff.derivative(y, 0) == 1 # expect ∂(x)/∂x
+end