revise show methods for ComposedFunction

base/operators.jl

@@ -1035,20 +1035,25 @@ end
 ∘(f, g, h...) = ∘(f ∘ g, h...)
 
 function show(io::IO, c::ComposedFunction)
- if c.outer |> Symbol |> Base.isoperator
- print(io, '(', c.outer, ')')
- else
- show(io, c.outer)
- end
+ _showcomposed(io, c.outer)
  print(io, " ∘ ")
- show(io, c.inner)
+ _showcomposed(io, c.inner)
 end
 
+#shows !f instead of (!) ∘ f when ! is the outermost function
 function show(io::IO, c::ComposedFunction{typeof(!)})
- print(io, "!")
- show(io, c.inner)
+ print(io, '!')
+ _showcomposed(io, c.inner)
 end
 
+_showcomposed(io::IO, x) = show(io, x)
+#display operators like + and - inside parens
+_showcomposed(io::IO, f::Function) = isoperator(Symbol(f)) ? (print(io, '('); show(io, f); print(io, ')')) : show(io, f)
+#nesting for chained composition
+_showcomposed(io::IO, f::ComposedFunction) = (print(io, '('); show(io, f); print(io, ')'))
+#no nesting when ! is the outer function in a composition chain
+_showcomposed(io::IO, f::ComposedFunction{typeof(!)}) = (print(io, '!'); show(io, f.inner))
+
 """
  !f::Function
 
@@ -1070,9 +1075,7 @@ julia> filter(!isletter, str)
 ```
 """
 !(f::Function) = (!) ∘ f
-
-#allows !!f === f
-!(f::ComposedFunction{typeof(!)}) = f.inner
+!(f::ComposedFunction{typeof(!)}) = f.inner #allows !!f === f
 
 """
  Fix1(f, x)

base/show.jl

@@ -468,6 +468,20 @@ end
 show(io::IO, f::Function) = show_function(io, f, get(io, :compact, false)::Bool)
 print(io::IO, f::Function) = show_function(io, f, true)
 
+function show_function(io::IO, c::ComposedFunction, compact::Bool)
+ if compact
+ show(io, c)
+ else
+ print(io, "ComposedFunction(")
+ show_function(io, c.outer, false)
+ print(io, ", ")
+ show_function(io, c.inner, false)
+ print(io, ')')
+ end
+end
+
+show_function(io::IO, x, ::Bool) = show(io, x)
+
 function show(io::IO, f::Core.IntrinsicFunction)
  if !(get(io, :compact, false)::Bool)
  print(io, "Core.Intrinsics.")

test/operators.jl

@@ -180,6 +180,10 @@ end
  @test filter(!isuppercase, str) == replace(str, r"[A-Z]" => "")
  @test filter(!islowercase, str) == replace(str, r"[a-z]" => "")
  @test !!isnan === isnan
+ @test repr(!isnan) == "!isnan"
+ @test repr((-) ∘ sin) == "(-) ∘ sin"
+ @test repr(cos ∘ (sin ∘ tan)) == "cos ∘ (sin ∘ tan)"
+ @test repr(!(cos ∘ !sin)) == "!(cos ∘ !sin)"
 end
 
 # issue #19891