fix print_arg signature

Author: shashi

src/types.jl

@@ -422,7 +422,7 @@ end
 setargs(t, args) = Term{symtype(t)}(operation(t), args)
 cdrargs(args) = setargs(t, cdr(args))
 
-print_arg(io, x::Union{Complex, Rational}) = print(io, "(", x, ")")
+print_arg(io, x::Union{Complex, Rational}; paren=true) = print(io, "(", x, ")")
 isbinop(f) = istree(f) && Base.isbinaryoperator(nameof(operation(f)))
 function print_arg(io, x; paren=false)
     if paren && isbinop(x)
@@ -431,7 +431,7 @@ function print_arg(io, x; paren=false)
         print(io, x)
     end
 end
-print_arg(io, s::String) = show(io, s)
+print_arg(io, s::String; paren=true) = show(io, s)
 function print_arg(io, f, x)
     f !== (*) && return print_arg(io, x)
     if Base.isbinaryoperator(nameof(f))