Merge pull request #535 from JuliaSymbolics/myb/nanmath

Use NaNMath lowering by default

src/code.jl

@@ -1,6 +1,6 @@
 module Code
 
-using StaticArrays, LabelledArrays, SparseArrays, LinearAlgebra
+using StaticArrays, LabelledArrays, SparseArrays, LinearAlgebra, NaNMath, SpecialFunctions
 
 export toexpr, Assignment, (←), Let, Func, DestructuredArgs, LiteralExpr,
        SetArray, MakeArray, MakeSparseArray, MakeTuple, AtIndex,
@@ -96,7 +96,30 @@ Base.convert(::Type{Assignment}, p::Pair) = Assignment(pair[1], pair[2])
 
 toexpr(a::Assignment, st) = :($(toexpr(a.lhs, st)) = $(toexpr(a.rhs, st)))
 
-function_to_expr(op, args, st) = nothing
+const NaNMathFuns = (
+    sin,
+    cos,
+    tan,
+    asin,
+    acos,
+    acosh,
+    atanh,
+    log,
+    log2,
+    log10,
+    lgamma,
+    log1p,
+    sqrt,
+)
+function function_to_expr(op, O, st)
+    op in NaNMathFuns || return nothing
+    name = nameof(op)
+    fun = GlobalRef(NaNMath, name)
+    args = map(Base.Fix2(toexpr, st), arguments(O))
+    expr = Expr(:call, fun)
+    append!(expr.args, args)
+    return expr
+end
 
 function function_to_expr(op::Union{typeof(*),typeof(+)}, O, st)
     out = get(st.rewrites, O, nothing)

test/code.jl

@@ -189,6 +189,10 @@ test_repr(a, b) = @test repr(Base.remove_linenums!(a)) == repr(Base.remove_linen
         f = eval(toexpr(Func([a+b], [], a+b)))
         @test f(1) == 1
         @test f(2) == 2
+
+        f = eval(toexpr(Func([a, b], [], sqrt(a - b))))
+        @test isnan(f(0, 10))
+        @test f(10, 2) ≈ sqrt(8)
     end
 
     let